Contact method of solder strip and battery piece of back contact solar battery

Abstract

The invention relates to series connection of battery assemblies, in particular to a contact method of a welding strip and a battery piece of a back contact solar battery. The contact method of the welding strip and the battery piece of the back contact solar cell comprises the steps that insulation paste is arranged at the position, needing to be isolated, of the battery piece and the welding strip, conductive materials are arranged at the position, needing to be conducted, of the battery piece and the welding strip, then contact sites are formed, and the height of the contact sites is larger than that of the insulation paste; and fixing the welding strip on the surface of the battery piece, and realizing ohmic contact between the welding strip and the contact site through a subsequent lamination process to prepare the back contact solar battery module. A traditional high-temperature welding process is replaced by a crimping process, so that the bending of the back contact solar cell is not easily caused, and meanwhile, the over-welding risk is reduced; by preparing the contact site in advance and making the contact site higher than the insulation paste, the height difference between the grid line and the solder strip is eliminated, the pseudo soldering risk is reduced, and the yield and the service life of the assembly product are effectively improved.

Description

Technical Field

[0001] The invention relates to the series connection of battery components, and in particular to a method for contacting a welding strip of a back-contact solar cell with a battery sheet. Background Art

[0002] Back-contact solar cells move both the electron transport layer and the hole transport layer of the cell to the back of the cell, avoiding short-circuit current loss caused by electrode shielding. Therefore, this structure has the highest theoretical conversion efficiency of crystalline silicon single-junction cell technology, 29.1%. It is often used by researchers to break through the highest efficiency of single-crystalline silicon solar cells, and is also one of the cell routes that various manufacturers have laid out. However, at present, back-contact solar cells have not been mass-produced, and there are still some technical difficulties to be solved, especially how to achieve the series connection of back-contact solar cells to ensure the overall performance of the battery components.

[0003] The traditional method of connecting cells in series mainly uses solder welding technology, but this welding technology has the following problems, which restricts the reliability and cost-effectiveness of battery components:

[0004] (1) High welding temperature: Traditional welding solutions usually require high temperatures, which may cause bending and deformation of the back-contact solar cells. In addition, high-temperature welding also increases the risk of over-welding, thereby affecting the yield and service life of the product.

[0005] (2) Height difference of solder joints leads to cold solder joints: Since the adjacent positions of solder joints are usually covered with insulating glue, there is a certain height difference between the gate line and the solder strip; this height difference can easily cause cold solder joints at adjacent solder joints, which in turn leads to poor contact when the battery cells are connected in series. Summary of the invention

[0006] The purpose of the present invention is to solve the problems that the traditional method of connecting battery cells in series mainly adopts solder welding technology, which has the disadvantages of high welding temperature causing bending and deformation of the back-contact solar cell, affecting the yield and service life of the product, and the height difference of the solder joint causing cold solder joints, and to provide a contact method between the solder strip of the back-contact solar cell and the battery cell.

[0007] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions:

[0008] A method for contacting a soldering ribbon of a back-contact solar cell with a solar cell sheet is special in that it comprises the following steps:

[0009] Step 1: Print insulating glue at the position on the battery cell that needs to be isolated from the welding ribbon;

[0010] Step 2: a conductive material is arranged at a position on the battery cell that needs to be connected to the welding strip to form a contact point, and the height of the contact point is greater than the height of the insulating glue in step 1;

[0011] The conductive medium of the conductive material includes at least one of a metal-based conductive medium and a carbon-based conductive medium, the metal-based conductive medium includes at least one of tin, silver, copper, nickel, and aluminum, and the carbon-based conductive medium includes at least one of carbon black, graphite, carbon nanotubes, and graphene; for example, solder paste containing a metal-based conductive medium, conductive glue containing a metal-based conductive medium, conductive glue containing a carbon-based conductive medium, and conductive glue containing a metal-based conductive medium and a carbon-based conductive medium (mixed conductive medium);

[0012] Step 3, fixing a plurality of welding strips at preset positions of a plurality of battery cells obtained in step 2, and connecting the plurality of battery cells in sequence to obtain a battery string;

[0013] Step 4: Laminating the battery string obtained in step 3 with the packaging material so that each welding strip is in ohmic contact with the contact point to obtain a back-contact solar cell module.

[0014] Furthermore, the step 2 is specifically as follows: placing solder paste at the position on the battery cell that needs to be connected to the solder ribbon, heating the solder paste to melt it, and then cooling and solidifying it on the battery cell to form a contact point; the melting temperature is greater than the lamination temperature described in step 4.

[0015] Furthermore, in step 2, the time taken from melting to solidification is less than 5 seconds.

[0016] Furthermore, the step 2 is specifically as follows: applying conductive glue at the position on the battery cell that needs to be connected to the soldering tape, and curing the conductive glue at the corresponding position by heating, UV or other methods to form a contact point.

[0017] Further, the contact site width Z>2Y-X, and Z>0;

[0018] X is the width of the welding strip, and Y is the offset distance of the welding strip relative to the edge of the contact site in the direction of the welding strip width.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention provides a method for contacting a soldering ribbon of a back-contact solar cell with a cell. Since the height of the contact point is higher than the height of the insulating glue, the height of the soldering ribbon is also correspondingly higher. This enables the cell to be in close contact with the soldering ribbon during the lamination process, thereby avoiding the problem of cell bending and over-welding caused by excessively high welding temperature, thereby improving the reliability and life of the component.

[0021] (2) The present invention eliminates the height difference problem between the soldering ribbon and the soldering pad caused by the presence of the insulating glue in the traditional welding method by ensuring that the height of the contact point is higher than the height of the insulating glue. The present invention not only improves the tightness of the contact, but also ensures the stability of the electrical connection, thereby greatly improving the production yield and consistency of the product.

[0022] (3) The present invention realizes welding by utilizing pressure and temperature conditions during the lamination process. This integrated process not only simplifies the production process, but also reduces the dependence on special welding equipment, thereby reducing the equipment investment cost. In addition, production efficiency is also improved because a single process can complete multiple tasks at the same time, thereby improving the automation degree and economic benefits of the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a method for contacting a welding strip of a back-contact solar cell with a solar cell sheet according to the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of a battery cell provided with contact points and insulating glue obtained in step 3 of an embodiment of the present invention;

[0025] Figure 3 for Figure 2 AA section view;

[0026] Figure 4 This is a schematic diagram of the partial structure of the battery string obtained in step 5 of the embodiment of the present invention;

[0027] Figure 5 for Figure 4 Enlarged view of point B in the middle.

[0028] The reference numerals are as follows: 1-contact site; 2-insulating glue; 3-grid line; 4-cell; 5-soldering strip. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0030] Embodiment 1

[0031] Reference Figure 1 A method for contacting a soldering ribbon of a back-contact solar cell with a cell sheet comprises the following steps:

[0032] Step 1. Reference Figures 2-3 , printing insulating glue 2 at the position on the battery cell 4 that needs to be isolated from the welding ribbon 5 (the position includes the gate line 3 that needs to be isolated from the welding ribbon 5 and the battery cell 4 around it); the printing width of the insulating glue 2 is greater than the width of the welding ribbon 5 in step 3;

[0033] Step 2: Place solder paste on the position on the cell 4 that needs to be connected to the solder ribbon 5 (the position includes the gate line 3 that needs to be connected to the solder ribbon 5 and the cell 4 around it), heat the solder paste to melt it, and then cool and solidify it on the cell 4 to form a contact point 1;

[0034] The height of the contact site 1 is greater than the height of the insulating glue 2 in step 1. For example, the height of the insulating glue 2 is 50 μm, and the height of the contact site 1 is 70 μm. In the welding process of the traditional back-contact solar cell, since the insulating glue 2 is arranged at the adjacent position of the welding point, there is a certain height difference between the grid line 3 and the welding strip 5 at this position, which is easy to cause a cold welding of the welding point. In the present invention, since the height of the contact site 1 is higher than the height of the insulating glue 2, the height difference between the welding strip 5 and the welding pad formed by the insulating glue 2 in the traditional welding method is eliminated, thereby avoiding the cold welding problem caused by this.

[0035] The width of the contact site 1 Z>2Y-X, and Z>0; X is the width of the welding strip 5, and Y is the offset distance of the welding strip 5 relative to the edge of the contact site 1 in the width direction of the welding strip 5, the purpose of which is to ensure that the welding strip 5 is always within the range of the conductive material no matter how it is offset, to ensure the conductivity and current transmission efficiency, optimize the material utilization rate, prevent short circuits and improve the structural stability, and ensure the performance and reliability of the battery cell 4 during the series connection process; for example, the width of the welding strip X is 3mm, the offset distance Y is 2mm, and the width of the contact site 1 is Z>1mm, so the width of the conductive material Z can be 1.5mm, 2mm, 3mm, etc.;

[0036] The melting temperature of the solder paste is higher than the lamination temperature in step 4. The traditional soldering solution requires the solder paste to be melted during the entire lamination process. If the heating time is too long, more silver will be dissolved into the tin, which may easily cause over-soldering. The present invention uses solder paste, and the melting temperature of the solder paste is higher than the lamination temperature. There is no problem of long-term solder paste melting, and over-soldering will not occur.

[0037] The time taken for solder paste to melt and solidify is less than 5 seconds. Rapid melting and solidification can effectively control welding quality, improve production efficiency, and reduce the risk of cold soldering and over soldering.

[0038] In other embodiments, step 2 may also be: placing a solder pad at a position on the battery cell 4 that needs to be connected to the solder ribbon 5 (the position includes the gate line 3 that needs to be connected to the solder ribbon 5 and the battery cell 4 around it), placing solder paste on each solder pad so that the solder paste completely covers the surface of the solder pad; heating the solder paste to melt it, and then cooling and solidifying it on the solder pad to form a contact site 1; the melting temperature is greater than the lamination temperature described in step 4;

[0039] Step 3: fix multiple welding strips 5 at corresponding positions of multiple battery cells 4 obtained in step 2 by bonding to obtain a battery string, such as Figures 4-5As shown; firstly bonding and fixing the soldering tape 5 can reduce the risk of soldering tape 5 displacement, cold soldering and soldering defects in step 4, and improve production efficiency and adapt to automated production;

[0040] Step 4, laminating the battery string obtained in step 4 with the packaging material, so that each welding ribbon 5 achieves ohmic contact with the contact site 1, and obtains a back-contact solar cell module; for traditional welding schemes, if the back-contact solar cell module has stress during use, it will cause the welding ribbon 5 to pull off the welding pad, thereby causing the back-contact solar cell module to fail. The present invention presses the welding ribbon 5 onto the raised contact site 1 through vacuuming during the lamination process, and maintains the pressure through elastic packaging materials, thereby solving the problem of welding pad falling off caused by stress and the failure of the back-contact solar cell module.

[0041] Embodiment 2

[0042] A method for contacting a soldering ribbon of a back-contact solar cell with a cell sheet comprises the following steps:

[0043] Step 1, printing insulating glue 2 at the position on the battery cell 4 that needs to be isolated from the welding ribbon 5 (the position includes the gate line 3 that needs to be isolated from the welding ribbon 5 and the battery cell 4 around it);

[0044] Step 2: Apply conductive glue to the position on the battery cell 4 that needs to be connected to the welding ribbon 5 (the position includes the grid line 3 that needs to be connected to the welding ribbon 5 and the battery cell 4 around it), and use thermal curing or ultraviolet curing to cure the conductive glue at the corresponding position to form a contact site 1; the conductive glue can be one of a conductive glue containing a metal-based conductive medium, a conductive glue containing a carbon-based conductive medium, and a conductive glue containing a metal-based conductive medium and a carbon-based conductive medium (a mixed conductive medium);

[0045] The width of the contact site 1 Z>2Y-X, and Z>0; X is the width of the soldering strip 5, and Y is the offset distance of the soldering strip 5 relative to the edge of the contact site 1 in the width direction of the soldering strip 5, in order to ensure the conductivity, stability and fault tolerance of the welding area, while taking into account the economy of material use and the operability of the production process; for example, the width X of the soldering strip 5 is 8mm, the offset distance Y is 2mm, the width of the thermal conductive material is Z>-4mm, and Z>0, so the width Z of the conductive material can be 0.5mm, 1mm, 2mm, etc.;

[0046] The rest of the configuration of this embodiment is consistent with that of the first embodiment.

Claims

1. A method for contacting a back contact solar cell welding strip with a solar cell, characterized in that: The steps include: Step 1: Printing insulating glue (2) at a position on the battery cell (4) that needs to be isolated from the welding strip (5); Step 2: placing a conductive material at a position on the battery cell (4) that needs to be connected to the welding strip (5) to form a contact point (1), wherein the height of the contact point (1) is greater than the height of the insulating glue (2) in step 1; The conductive medium of the conductive material includes at least one of a metal-based conductive medium and a carbon-based conductive medium, the metal-based conductive medium includes at least one of tin, silver, copper, nickel, and aluminum, and the carbon-based conductive medium includes at least one of carbon black, graphite, carbon nanotubes, and graphene; Step 3, fixing a plurality of welding strips (5) at preset positions of a plurality of battery cells (4) obtained in step 2, and connecting the plurality of battery cells (4) in sequence to obtain a battery string; Step 4: Laminating the battery string obtained in step 3 with the packaging material, so that each welding strip (5) and the contact point (1) achieve ohmic contact, and obtain a back-contact solar cell module.

2. The method for contacting a back contact solar cell welding strip with a solar cell according to claim 1, characterized in that: The step 2 specifically comprises: placing solder paste at a position on the battery cell (4) that needs to be connected to the solder strip (5), heating the solder paste to melt it, and then cooling and solidifying it on the battery cell (4) to form a contact point (1); the melting temperature is greater than the lamination temperature in step 4.

3. The method for contacting a back contact solar cell welding strip with a solar cell according to claim 2, characterized in that: In step 2, the time from melting to solidification is less than 5 seconds.

4. The method for contacting a back contact solar cell welding strip with a solar cell according to claim 1, characterized in that: The step 2 specifically comprises: applying conductive glue at the position on the battery cell (4) that needs to be connected to the solder strip (5), and solidifying the conductive glue at the corresponding position to form a contact point (1).

5. A method for contacting a back contact solar cell welding strip with a solar cell according to any one of claims 1 to 4, characterized in that: The contact site (1) has a width Z>2Y-X, and Z>0; X is the width of the welding strip (5), and Y is the offset distance of the welding strip (5) relative to the edge of the contact point (1) in the width direction of the welding strip (5).

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