Welding structure of solar cell and back contact solar cell

Abstract

The utility model discloses a welding structure of a solar cell sheet and a back contact solar cell, the welding structure of the solar cell sheet is used for connecting the cell sheet and a welding strip, the welding structure of the solar cell sheet comprises a bonding pad arranged on the cell sheet, an insulating part and a conductive member, the insulating part covers the bonding pad, the insulating part comprises a plurality of through holes, and the conductive member is arranged on the bonding pad. Conductive pieces are arranged in the at least two through holes, and the conductive pieces are conductively connected to the bonding pads and welded to the welding strips. According to the utility model, the laying precision of the welding strip during welding can be improved, so that the welding reliability is improved.

Description

Technical Field

[0001] This utility model relates to the field of solar cell technology, specifically to a welding structure for solar cells and a back-contact solar cell. Background Technology

[0002] Solar cells are the core of photovoltaic modules, responsible for converting light energy into electrical energy. Conductive grid lines on the solar cells collect current and transmit it to solder pads. The solder pads are bonded to solder ribbons using conductive material, ensuring current transfer from the cells to the ribbons. The solder ribbons are used to connect cells in series or parallel to form a circuit. In existing technologies, solder paste is commonly used as the conductive material, and individual solder paste points are used. When solder paste melts, it forms an arc-shaped structure, making it prone to misalignment when the solder ribbon is laid on it. This reduces the effective soldering area and affects the reliability of soldering at the solder joint. Utility Model Content

[0003] To address the aforementioned technical problems, this invention provides a welding structure for solar cells and a back-contact solar cell, which can improve the laying accuracy of the welding strips and thus enhance the reliability of the welding process.

[0004] The specific technical solution provided by this utility model is as follows:

[0005] In a first aspect, a welding structure for a solar cell is provided for connecting a solar cell and a solder strip. The welding structure for the solar cell includes a solder pad, an insulating part, and a conductive element disposed on the solar cell. The insulating part covers the solder pad and includes a plurality of through holes. At least two through holes are provided with conductive elements, which are electrically connected to the solder pad and welded to the solder strip.

[0006] As a preferred embodiment of the above solution, the insulating portion includes a pressing portion and an interconnect portion. The pressing portion is disposed at the edge of the pad, and the interconnect portion is disposed between the through holes. The interconnect portion and the pressing portion form a mesh structure.

[0007] As a preferred embodiment of the above scheme, the width of the pressing edge is less than or equal to the width of the interconnection part.

[0008] As a preferred embodiment of the above scheme, the pad includes a protrusion located within a through-hole, the height of which is greater than the height of the pad covered by the insulating portion; and / or, the height H1 of the protrusion is 5-15 μm, and the height H2 of the pad covered by the insulating portion is 3-10 μm.

[0009] As a preferred embodiment of the above scheme, the conductive components are evenly distributed on the pads.

[0010] As a preferred embodiment of the above scheme, the conductive component is made of tin-based solder, and the tinning temperature of the conductive components in at least two through holes is different.

[0011] As a preferred embodiment of the above scheme, there is a distance between the conductive component and the inner wall of the through hole before the tin is melted.

[0012] As a preferred embodiment of the above scheme, the height of the conductive part is greater than or equal to the height of the insulating part.

[0013] As a preferred embodiment of the above scheme, the insulating portion also covers the battery cell around the solder pad.

[0014] Secondly, a back-contact solar cell is provided, comprising a solar cell and a welding structure for the solar cell as described above.

[0015] This invention features an insulating portion with multiple through-holes on the pad, and at least two of these through-holes contain conductive elements. These conductive elements are electrically connected to the pad and welded to the solder strip. This provides multi-point support for the conductive elements during solder strip laying, making the laying more stable and improving the reliability of the solder strip welding. Furthermore, the insulating portion of this invention includes a pressing edge portion and an interconnecting portion. The pressing edge portion is located at the edge of the pad, and the interconnecting portion is located between the through-holes. The interconnecting portion and the pressing edge portion form a mesh structure, pressing the pad onto the surface of the solar cell, thereby improving the bonding strength between the pad and the solar cell and better resisting the risk of pad desoldering under high temperature and high humidity environments.

[0016] Furthermore, since the pads covered by the insulating portion do not need to contact the solder, the intermetallic compound layer (IMC layer) will not thicken. This invention, by setting the height of the pads within the through-holes to be greater than the height of the pads covered by the insulating portion, allows for a thinner silver layer on the pads covered by the insulating portion, thereby reducing silver consumption. In addition, this invention also prevents cold solder joints caused by unstable temperature fields within the soldering chamber during the soldering process by combining multiple conductive materials with different soldering temperatures within at least two through-holes. Attached Figure Description

[0017] The accompanying drawings are provided to better understand this utility model and do not constitute an undue limitation thereof. Wherein:

[0018] Figure 1 This is a schematic diagram of the solder joint and solder ribbon laying structure on the solder pad in the prior art;

[0019] Figure 2 This is a schematic diagram of the welding structure of the solar cell in this utility model;

[0020] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure along line AA;

[0021] Figure 4This is a structural schematic diagram of one arrangement of the conductive component inside the through hole in this utility model;

[0022] Figure 5 This is a schematic diagram of the structure of the present invention, in which two conductive materials are disposed within the through hole;

[0023] Figure 6 This is a schematic diagram of the back-contact solar cell in this utility model.

[0024] The above figures include the following reference numerals:

[0025] 1. Pad; 10. Conductive material; 20. Insulating adhesive; 100. Battery cell; 101. Main grid line; 102. Conventional fine grid line; 103. Irregular fine grid line; 200. Solder strip; 11. Protrusion; 2. Insulating part; 21. Pressing edge; 22. Interconnection part; 3. Conductive component; 31. First conductive material; 32. Second conductive material; 4. Through hole. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0027] As described in the background art, conductive grid lines on a solar cell are used to collect current and transmit it to the pads. The conductive grid lines are divided into main grid lines and fine grid lines. The fine grid lines collect the current on the surface of the cell and transmit it to the main grid lines. The main grid lines concentrate the current and transmit it to the pads. The pads form solder joints on the pads through conductive materials. The solder joints are welded to the solder ribbon to ensure that the current is transmitted from the cell to the solder ribbon. The solder ribbon is used to connect the cells in series or in parallel to form a circuit, ensuring that the current is led out from the cell and transmitted to the external circuit.

[0028] In existing technologies, the commonly used conductive material 10 is solder paste. The conductive material is first printed onto the pads using a stencil, and then heated to thoroughly bake the solvent within the solder paste, achieving a molten solder state. For example... Figure 1 As shown, the existing battery cell 100 is provided with a pad 1 and an insulating adhesive 20. A single solder paste is usually used as a soldering point on the pad 1. When the solder paste melts, it has an arc-shaped structure. When the solder ribbon 200 is laid on the solder paste, it is easy for the position to shift, resulting in a reduction in the effective soldering area and affecting the reliability of the solder ribbon 200 in the soldering point.

[0029] Furthermore, the insulating adhesive 20 on the surface of the back contact solar cell is formed by screen printing. After printing, the insulating adhesive 20 is cured by heating or ultraviolet light to obtain a back contact solar cell with insulating adhesive 20. When the back contact solar cells are connected in series to form a photovoltaic module, flat solder ribbons are usually used to connect adjacent cells. At the same time, the solder ribbon 200 is only soldered to the electrode on the back of the cell. This welding method allows the solder ribbon 200 to form a firm connection with the cell electrode on one side, while the other side is not directly welded or in contact with other components, resulting in the cell being subjected to stress on one side. Therefore, after high temperature, high humidity, and high and low temperature alternating reliability tests, the solder joint at the solder pad 1 is prone to detachment.

[0030] Furthermore, the material of pad 1 is typically silver. After the tin in the conductive material 10 alloys with silver, an IMC layer (intermetallic compound layer) is formed. Tin continuously reacts with silver, leading to an increase in the thickness of the IMC layer and further alloying of the silver. This thickening of the IMC layer can cause brittle fracture of the solder joint. Therefore, the silver in pad 1 needs to have a certain thickness to resist the aforementioned alloying process. However, in the prior art, the areas on pad 1 covered by insulating adhesive 20 (i.e., areas that do not need to contact tin) and the solder joints (i.e., areas that need to contact tin) are usually set to the same silver layer thickness, resulting in a waste of silver material on pad 1. At the same time, during the soldering of the battery cell 100, due to the unstable temperature field inside the infrared soldering chamber, the tin-based solder of the conductive material 10 may not reach a certain tinning temperature, causing the tin and silver to fail to alloy, resulting in poor soldering of the solder strip 200.

[0031] To address the aforementioned technical problems, this utility model provides a welding structure for solar cells and a back-contact solar cell, which improves the laying accuracy of the solder strip during welding, thereby enhancing welding reliability. It also better resists the risk of solder pad detachment under high temperature and high humidity environments, as well as the risk of incomplete soldering due to unstable temperature fields. Furthermore, it reduces the silver consumption of the solder pads.

[0032] Example 1

[0033] like Figure 2 , Figure 3 As shown, this utility model provides a welding structure for a solar cell, used to connect a solar cell 100 and a welding strip 200. The welding structure for the solar cell includes a welding pad 1, an insulating part 2, and a conductive element 3 disposed on the solar cell 100. The insulating part 2 covers the welding pad 1 and includes a plurality of through holes 4. At least two through holes 4 are provided with conductive elements 3. The conductive elements 3 are electrically connected to the welding pad 1 and welded to the welding strip 200.

[0034] Specifically, the insulating part 2 is an insulating layer on the battery cell 100, specifically an insulating adhesive. The insulating adhesive is used to isolate electrical contact between battery cells 100 or between battery cells 100 and other metal parts to prevent short circuits. The insulating part 2 on the pad 1 is provided with at least two through holes 4, and adjacent through holes 4 are separated by the insulating part 2. At the same time, conductive elements 3 are provided on the pad 1 at at least two through holes 4, thus forming distributed solder points on the pad 1. This forms multi-point support when the solder ribbon 200 is laid, making the solder ribbon 200 lay more stable, increasing the welding area, and improving the reliability of solder ribbon 200 welding.

[0035] like Figure 4 As shown, in one embodiment, conductive elements 3 can be provided on the pads 1 in some of the through holes 4, while the other part of the through holes 4 is left unused. The conductive elements 3 are evenly distributed on the pads 1, so that the conductive elements 3 can be evenly supported on the bottom of the solder strip 200 corresponding to the pads 1, further improving the stability of the solder strip 200 during laying.

[0036] The shape of the through-hole 4 includes, but is not limited to, one or a combination of at least two of the following: rectangular, circular, and polygonal. That is, the insulating part 2 can be formed into various shapes on the pad 1 according to actual needs, and the shapes of the multiple through holes 4 can be the same or different.

[0037] The vias 4 are arranged in an array on the pads 1. The array includes one or a combination of at least two of the following: linear array, planar array, and grid array. That is, the vias 4 can be arranged in various shapes according to actual needs, including but not limited to the array distribution mentioned above, or other required arrangements.

[0038] In one implementation, such as Figure 2As shown, the vias 4 are distributed in a planar array or grid array on the pads 1, and the vias are rectangular. There are 9 vias 4 on the pads 1. The insulating portion 2 on the pads 1 includes a pressing portion 21 and an interconnect portion 22. The connection method of the pressing portion 21 and the interconnect portion 22 includes, but is not limited to, integral molding, and integral molding is carried out by injection molding. The pressing portion 21 is set at the edge of the pads 1, that is, the pressing portion 21 is set around the edge of the pads 1 outside the vias 4. The width of the pressing portion 21 is equal in both the horizontal and vertical directions. The pressing portion 21 seals the edge of the pads 1, which can prevent moisture from penetrating from the edge of the pads 1 to the bottom of the pads 1 under high temperature and high humidity environment, so as to prevent the pads 1 from desoldering. The interconnect portion 22 is set between the vias 4. Specifically, the interconnect portion 22 is set between adjacent vias 4, including vertically adjacent, horizontally adjacent, and diagonally adjacent vias 4. The interconnect portion 22 has an approximately "grid"-shaped mesh structure, and the width of the interconnect portion 22 is equal in both the horizontal and vertical directions. The interconnecting part 22 and the pressing part 21 together form a pressing mesh structure, pressing the pad 1 onto the surface of the cell 100, which improves the bonding force between the pad 1 and the cell 100 and can better resist the risk of the pad 1 desoldering under high temperature and high humidity conditions.

[0039] Furthermore, the width of the pressing portion 21 is less than or equal to the width of the interconnect portion 22. Specifically, as shown... Figure 2 As shown, the width W1 of the pressing portion 21 is 10-100μm, for example, 10μm, 50μm, or 100μm, preferably 50μm, and the width W2 of the interconnect portion 22 is 50-100μm, for example, 50μm, 70μm, or 100μm, preferably 70μm. This increases the area of ​​the insulating portion 2 in the middle of the pad 1, further improving the bonding force between the pad 1 and the battery cell 100.

[0040] like Figure 3 As shown, the pad 1 includes a protrusion 11 located within the through-hole 4, meaning the height of the pad 1 within the through-hole 4 is greater than the height of the pad 1 covered by the insulating portion 2. Specifically, as... Figure 2 As shown, the height H1 of the protrusion 11 is 5-15 μm, for example, 5 μm, 10 μm, or 15 μm, preferably 10 μm. The height H2 of the pad 1 covered by the insulating portion 2 is 3-10 μm, for example, 3 μm, 6 μm, or 10 μm, preferably 6 μm. The pad 1 covered by the insulating portion 2 does not need to be in contact with solder, and there is no IMC layer thickening phenomenon. Therefore, the silver layer of the pad 1 covered by the insulating portion 2 can be set to be thinner, thereby reducing the silver consumption of the pad 1.

[0041] Conductive component 3 is a conductive material of tin-based solder. Confined within the through-hole 4, conductive component 3 effectively prevents it from dispersing during the soldering process. The soldering temperatures of conductive components 3 within at least two through-holes 4 are different; that is, at least two conductive materials with different soldering temperatures are present within the through-holes 4. The specific soldering temperatures and the placement of the conductive materials within the through-holes 4 can be determined based on the actual temperature field conditions within the soldering chamber. Figure 5 As shown, a first conductive material 31 and a second conductive material 32 with different tin-melting temperatures are disposed within the through-hole 4. This combination of multiple conductive materials with different tin-melting temperatures helps prevent cold solder joints caused by unstable temperature fields within the soldering chamber during the soldering process.

[0042] like Figures 2 to 6 As shown, there is a distance between the conductive component 3 and the inner wall of the through-hole 4 before soldering. That is, when the conductive component 3 is printed onto the pad 1 inside the through-hole 4, the conductive component 3 and the inner wall of the through-hole 4 have a clearance fit. This provides extension space for the conductive component 3 during soldering, thus confining the conductive component 3 within the through-hole 4.

[0043] like Figure 3 As shown, the height of the conductive element 3 is greater than or equal to the height of the insulating part 2. This ensures that the upper end of the conductive element 3 is not lower than the upper end of the insulating part 2, facilitating welding between the conductive element 3 and the solder strip 200.

[0044] like Figure 2 As shown, in this embodiment, the insulating portion 2 also covers the battery cell 100 surrounding the solder pad 1, thus further sealing the edge of the solder pad 1 in all directions and further resisting the risk of solder pad 1 desoldering under high temperature and high humidity environments. Figure 2 , Figure 6 As shown, the insulating part 2 also covers the fine grid line connected to the edge of the pad 1, thus preventing acidic substances in the conductive part 3 from corroding the silver paste of the fine grid line.

[0045] This invention first involves screen printing the insulating part 2 onto the battery cell 100, covering the pad 1 and surrounding it. The insulating part 2 on the pad 1 has multiple through holes 4. Then, the insulating part 2 is cured by heating or ultraviolet light to obtain the battery cell 100 with the insulating part 2. Next, conductive elements 3 are printed using a stencil, and the conductive elements 3 fall into the multiple through holes 4. Finally, solder ribbon 200 is laid on the conductive elements 3, and the conductive elements 3 are welded to the solder ribbon 200. Even if the soldering point of each conductive element 3 becomes arc-shaped after melting tin, the multi-point support formed by the conductive elements 3 can make the solder ribbon 200 more stable and accurate during laying, thereby improving the reliability of the solder ribbon 200 welding.

[0046] Example 2

[0047] like Figure 6As shown, this utility model provides a back-contact solar cell, including a solar cell 100 and a welding structure of the solar cell as described in Embodiment 1.

[0048] The solar cell 100 includes a positive electrode and a negative electrode, both of which are located on the back side of the back-contact solar cell. Both the positive and negative electrodes include a main grid line 101 and a fine grid line. The fine grid line connects to the main grid line 101. Considering the maximization of current collection efficiency, the adaptation of solar cell manufacturing processes, and the integration requirements of photovoltaic modules, the pad 1 is usually located at the end of the main grid line 101. The fine grid line includes a conventional fine grid line 102 and an irregular fine grid line 103. The insulating part 2 of the welding structure of the solar cell 100 also covers the irregular fine grid line 103 on the side of the positive and negative electrodes.

[0049] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A welding structure for solar cells, used to connect solar cells and solder strips, characterized in that, The welding structure of the solar cell includes a pad, an insulating part, and a conductive element disposed on the cell. The insulating part covers the pad and includes a plurality of through holes. The conductive element is disposed in at least two of the through holes and is electrically connected to the pad and welded to the solder strip.

2. The welding structure of the solar cell according to claim 1, characterized in that, The insulating portion includes a pressing portion and an interconnect portion. The pressing portion is disposed at the edge of the pad, and the interconnect portion is disposed between the through holes. The interconnect portion and the pressing portion form a mesh structure.

3. The welding structure of the solar cell according to claim 2, characterized in that, The width of the pressing edge is less than or equal to the width of the interconnection part.

4. The welding structure of the solar cell according to claim 1, characterized in that, The pad includes a protrusion located within the through hole, and the height of the protrusion is greater than the height of the pad at the location covered by the insulating portion. And / or, the height H1 of the protrusion is 5-15 μm, and the height H2 of the pad covered by the insulating portion is 3-10 μm.

5. The welding structure of the solar cell according to claim 1, characterized in that, The conductive elements are evenly distributed on the pads.

6. The welding structure of the solar cell according to claim 1, characterized in that, The conductive element is made of tin-based solder, and the tin melting temperature of the conductive element in at least two of the through holes is different.

7. The welding structure of the solar cell according to claim 6, characterized in that, There is a distance between the conductive element and the inner wall of the through hole before the tin is applied.

8. The welding structure of the solar cell according to claim 1, characterized in that, The height of the conductive element is greater than or equal to the height of the insulating part.

9. The welding structure of the solar cell according to claim 1, characterized in that, The insulating portion also covers the battery cell surrounding the solder pad.

10. A back-contact solar cell, characterized in that, Includes solar cells and the welded structure of solar cells as described in any one of claims 1-9.

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