A kind of buffer glue for solar cell sheet lamination and its lamination welding method

Abstract

The application discloses a kind of buffer glue for solar cell piece lamination and its lamination welding method.The buffer glue includes vinyl siloxane base polymer 30 to 60 parts by mass, hydrogen-containing polysiloxane crosslinking agent 1 to 10 parts, thermal tack-reducing modifier 15 to 45 parts, catalyst 0.05 to 2 parts.The lamination welding method coats the buffer glue on the first cell piece edge or the corresponding surface of the welding ribbon to be welded to form a buffer glue layer, places the second cell piece and the first cell piece in a lamination manner to make the buffer glue layer in the clamping interval, then sends it into the welding equipment for heating, and simultaneously completes the high-temperature addition curing of the buffer glue layer using the welding heat while completing the welding of the welding ribbon and the electrode.The application overcomes the technical problems of low tolerance error rate of traditional buffer glue printing, the need for additional curing station, and the difficulty of non-destructive repair and disassembly after curing, and can realize non-destructive repair of defective cell pieces.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell packaging and manufacturing technology, and more specifically to a buffer adhesive for stacking solar cells and a method for stacking and welding the same. Background Technology

[0002] As the photovoltaic industry evolves towards high-density and high-power modules, negative-pitch cascading technology has been widely adopted due to its ability to eliminate gaps between cells and significantly increase the light-receiving area. In negative-pitch cascading, the edges of adjacent cells partially overlap in the vertical projection direction, and metal solder strips are arranged within the overlapping area to connect the adjacent cells. To avoid rigid compression of the cell edges by the solder strips during subsequent welding and module lamination processes, and to reduce the risk of microcracks and breakage in the cells, a buffer adhesive layer is typically placed between the solder strips and the overlapping area of ​​the cells.

[0003] Existing buffer adhesives mostly use UV-curable adhesives or conventional addition-cure silicone. The typical process involves: first, printing the adhesive onto the edge of the solar cell; then pre-curing it using a dedicated UV irradiation station or heated drying tunnel; finally, stacking and welding the cured solar cells with a negative pitch. This type of process has the following technical drawbacks:

[0004] First, the buffering and protective effect is highly dependent on the printing uniformity of the adhesive layer. If there are fluctuations in the height of the adhesive dots or misalignment during the printing process, the cured adhesive dots will be difficult to compensate for with plastic flow, which can easily lead to stress concentration under the stress of stacking and lamination, thus increasing the microcrack failure rate of the solar cells.

[0005] Secondly, the production line must be equipped with separate curing equipment and curing stations, which increases equipment investment costs, production line space requirements, and overall production cycle time.

[0006] Third, if the solution of uncured stacking followed by curing is adopted directly, the existing adhesive material forms a strong chemical bond with the surface of the cell and solder ribbon after curing. When the cell string has poor soldering, misalignment, or microcracks and needs to be repaired, it is difficult to peel off the cell without damage. Forced disassembly can easily cause large-area damage to the silicon wafer, resulting in material waste and increased repair costs.

[0007] Therefore, it is necessary to propose a buffer adhesive for solar cell stacking and a stacking welding method to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of low tolerance rate in the printing of buffer adhesive, the need for additional curing stations, and the difficulty in non-destructive disassembly and rework after curing in the prior art.

[0009] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0010] A buffer adhesive for stacking solar cells, comprising the following components by weight:

[0011] 30 to 60 parts of vinylsiloxane-based polymer;

[0012] 1 to 10 parts of hydrogen-containing polysiloxane crosslinking agent;

[0013] 15 to 45 parts of a heat-resistant anti-tack modifier, wherein the heat-resistant anti-tack modifier is an organosilicon-modified resin with high-temperature molecular chain rearrangement or phase separation characteristics.

[0014] Catalyst 0.05 to 2 parts.

[0015] Further, the vinyl siloxane base polymer includes vinyl-terminated polydimethylsiloxane and vinyl MQ resin; by mass parts, the vinyl-terminated polydimethylsiloxane is 30 to 50 parts, the vinyl MQ resin is 10 to 20 parts, and the sum of the mass parts of the two is 30 to 60 parts.

[0016] Furthermore, the heat-reducing viscosity modifier is selected from one or more of polyester-modified silicone resin, polyethylene glycol-modified silicone resin, terminal long-chain alkyl-modified silicone resin, and fluoroalkyl-modified silicone resin.

[0017] Furthermore, the vinyl-terminated polydimethylsiloxane has a dynamic viscosity of 8000 to 25000 mPa·s at 25°C; the vinyl MQ resin has a dynamic viscosity of 10000 to 35000 mPa·s at 25°C; and the hydrogen content of the hydrogen-containing polysiloxane crosslinking agent is 0.3% to 2.5% by mass.

[0018] Furthermore, the catalyst is selected from one of platinum-vinylsiloxane complex, platinum-cyclopentadienyl complex, or chloroplatinic acid-alcohol complex; the buffer gel also includes 0.01 to 1 part of inhibitor, which is selected from one of methylbutynol, phenylbutynol, 3,5-dimethyl-1-hexyn-3-ol, or ethynylcyclohexanol.

[0019] Furthermore, the buffer adhesive also includes 1 to 15 parts of reinforcing filler, wherein the reinforcing filler has a specific surface area of ​​100 to 350 m². 2 / g of fumed silica; the buffer adhesive also includes 0.1 to 3 parts of silane coupling agent, wherein the silane coupling agent is selected from γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane or vinyltrimethoxysilane.

[0020] Furthermore, the buffer adhesive also includes one or more of a rheology modifier, a light stabilizer, or an antioxidant, with an addition amount of 0.1 to 2 parts by weight.

[0021] Furthermore, the Shore hardness of the cured buffer adhesive is 20 to 60A, and after being heated at a temperature not lower than 200°C for 30 to 60 seconds, the 180-degree peel strength between the adhesive layer and the surface of the battery cell substrate is reduced by more than 80% compared with the normal temperature state.

[0022] Furthermore, the cured buffer adhesive has a Shore hardness of 25 to 35A and a light transmittance of greater than 90% in the wavelength range of 380 to 1100 nm.

[0023] The present invention also includes a pre-coated adhesive solder ribbon, wherein the buffer adhesive is pre-coated on a portion or the entire surface of the metal solder ribbon for direct use during the stacking and packaging process.

[0024] The present invention also provides a buffer adhesive for stacking solar cells and a method for stacking and welding the same, using the aforementioned buffer adhesive or pre-coated adhesive strip, and comprising the following steps:

[0025] Step 1, Applying adhesive or providing pre-coated solder ribbon: Apply the buffer adhesive to the edge welding area of ​​the first cell or the surface of the solder ribbon to be welded to form a buffer adhesive layer, or directly provide pre-coated solder ribbon with the buffer adhesive layer pre-coated;

[0026] Step 2, Stacking: Stack the second battery cell with the first battery cell in a stacking manner, so that the buffer adhesive layer and the solder ribbon are in the stacking and clamping area between the first battery cell and the second battery cell to form a battery string;

[0027] Step 3, simultaneous welding and curing: The battery string is fed into the welding equipment for heating. While the welding strip and the battery cell electrode are being welded, the heat from the welding process is used to simultaneously complete the high-temperature addition curing of the buffer adhesive layer.

[0028] Step 4, Encapsulation: The welded battery strings are laminated to obtain photovoltaic modules.

[0029] Furthermore, in step one, the adhesive application method is selected from one of the following: steel plate printing, screen printing, piezoelectric jet dispensing, pneumatic dispensing, or roller coating.

[0030] Furthermore, the buffer adhesive layer is arranged in the form of discrete adhesive dots, continuous adhesive strips, or an array pattern directly below the solder strip. The length of the buffer adhesive layer is not less than 1.2 mm, the width is 0.3 to 0.8 mm, and the coating height is 0.20 to 0.40 mm.

[0031] Furthermore, in step three, the heat source of the welding equipment is selected from one of the following: infrared lamp box heat radiation source, hot air convection source, hot press welding head, or induction heating source.

[0032] Furthermore, in step three, welding and curing are carried out using infrared lamp box thermal radiation. The peak temperature of the welding area is 160 to 185°C, and the heating time in the range of 170 to 185°C is 1 to 3 seconds.

[0033] Furthermore, if the battery string has defects, a rework and disassembly step is performed, which includes:

[0034] The area to be repaired in the defective battery string is heated so that the buffer adhesive layer at the battery cell to be disassembled is heated to above 200°C and maintained for 30 to 60 seconds, inducing a heat-reducing and anti-sticking effect.

[0035] Separate the battery cells to be disassembled from the battery string;

[0036] The buffer adhesive is reapplied to the new replacement cell or solder strip, and the cells are stacked and then heated and welded again for simultaneous curing.

[0037] In the rework and disassembly step, a constant temperature heating table, soldering gun, hot air blowing, infrared radiation source or electromagnetic induction heating source are used to locally heat the area to be reworked.

[0038] The present invention also provides a solar cell string manufactured by the above-described stacking welding method, and a photovoltaic module comprising the solar cell string or a buffer adhesive layer formed after the buffer adhesive has been cured.

[0039] The present invention has the following beneficial effects:

[0040] First, by introducing a modified resin with high-temperature molecular chain rearrangement or phase separation characteristics into the organosilicon matrix, the material has suitable adhesive strength and elastic modulus at room temperature and conventional welding curing temperature. It can form a flexible wrapping of the solder ribbon during the stacking and lamination process, dispersing local mechanical stress. Under high temperature above 200°C, the modified chain segments undergo phase separation and molecular chain rearrangement with the organosilicon skeleton, which reduces the adhesion force between the adhesive layer and the cell interface by more than 80%, enabling the complete and undamaged peeling of defective cells, significantly improving rework efficiency and reducing material loss.

[0041] Secondly, by adopting a process route of stacking cells first and then welding and curing simultaneously, the uncured colloid can undergo adaptive microflow and spreading under the mechanical stacking and clamping action of two adjacent cells, effectively compensating for the height and position tolerances in the dispensing or printing process, making the stress distribution under the solder strip more uniform, and the zero microcrack rate of the cells after module lamination can reach more than 89%.

[0042] Third, the catalyst and inhibitor in the formula synergistically regulate the kinetics of the addition reaction, enabling the colloid to complete deep cross-linking in just 1 to 3 seconds under heating conditions of 160 to 185°C. This is highly consistent with the time cycle of conventional battery string welding stations, eliminating the need to add an extra UV curing light box or hot drying tunnel to the production line, thus reducing equipment investment and workshop floor space.

[0043] Fourth, this invention expands the adaptability of the adhesive application carrier and process. The buffer adhesive can be directly printed on the surface of the battery cell or pre-coated on the surface of the solder ribbon to form a pre-coated solder ribbon. At the same time, it is compatible with various welding methods such as infrared, hot air, hot pressing and induction heating, which greatly improves its applicability in different photovoltaic automated production lines. Attached Figure Description

[0044] Figure 1 A schematic diagram of the negative spacing stacking structure of photovoltaic cells and the location of adhesive dots;

[0045] Figure 2 This is a schematic diagram of the infrared welding synchronous curing process.

[0046] Figure 3 This is a schematic diagram of the high-temperature rework process for disassembling a component.

[0047] Figure 4 This is a side view of a partially pre-coated solder strip structure (with adhesive applied to the lower surfaces at both ends of the solder strip).

[0048] Explanation of reference numerals in the attached drawings: 1. First solar cell; 2. Second solar cell; 3. Solder strip; 4. Buffer adhesive dot; 5. Infrared light box radiation source; 6. Heating and splitting tool; 7. Pre-coated buffer adhesive layer. Detailed Implementation

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] This embodiment provides a buffer adhesive for stacking solar cells and a method for stacking and welding them.

[0052] The raw material composition of this cushioning adhesive, by parts by weight, includes:

[0053] 35 parts of vinyl-terminated polydimethylsiloxane with a dynamic viscosity of 20000 mPa·s at 25°C;

[0054] 15 parts of vinyl MQ resin with a dynamic viscosity of 25000 mPa·s at 25°C;

[0055] Two parts of hydrogen-containing polysiloxane with a hydrogen content of 1.2% by mass;

[0056] 23 parts of polyester-modified silicone resin;

[0057] 0.5 parts of platinum-vinylsiloxane complex;

[0058] 0.06 parts of methylbutynol, an alkynol inhibitor;

[0059] Specific surface area is 200m² 2 5 parts of fumed silica per g;

[0060] 1.5 parts of silane coupling agent γ-glycidyl oxypropyltrimethoxysilane.

[0061] The preparation method of the above-mentioned buffer gel includes the following steps:

[0062] The first step involves adding vinyl-terminated polydimethylsiloxane, vinyl MQ resin, polyester-modified silicone resin, hydrogen-containing polysiloxane, silane coupling agent, and 2.5 parts of fumed silica with a specific surface area of ​​200 m² / g into a planetary mixer according to the predetermined mass proportions. The mixture is stirred at 500 rpm for 15 minutes at room temperature to initially disperse the materials evenly.

[0063] The second step involves adding the remaining 2.5 parts of fumed silica with a specific surface area of ​​200 m² / g to the mixer, starting the vacuum degassing system to evacuate the system until the internal vacuum level is no higher than -0.09 MPa, maintaining this vacuum level to remove trace amounts of moisture and air from the material, and then filling the mixing vessel with high-purity nitrogen to restore atmospheric pressure. Under the nitrogen protective atmosphere, the mixture is continuously stirred at 1000 rpm for 60 minutes to achieve homogeneous dispersion of the nanoscale filler.

[0064] The third step involves adding platinum-vinylsiloxane complex and methylbutyninol to the stirred tank. Circulating cooling water is then introduced to maintain the material temperature at 20°C. Stirring continues for 120 minutes under nitrogen protection to ensure the catalyst and inhibitor are evenly distributed in the matrix resin. The resulting product, a one-component buffer adhesive, is then discharged and packaged. This adhesive is stable for 6 months at -18°C and has a working life of at least 72 hours at room temperature (25°C).

[0065] The buffer adhesive prepared above is used to implement a buffer adhesive for stacking solar cells and a method for stacking and welding them. The specific steps are as follows:

[0066] Step S101, Applying buffer adhesive: The monocrystalline silicon photovoltaic cell is transported to the printing station, and a predetermined pattern of buffer adhesive dots 4 is printed on the edge welding area of ​​the light-receiving surface of the first cell 1 using a precision steel plate printing screen. The printed buffer adhesive dots 4 are positioned directly below the solder strip 3 to be welded, with a dot width of 0.55mm, a length of 1.8mm, a wet film height controlled at 0.25mm, and the distance between the outer edge of the adhesive dot and the edge of the cell slice maintained at 0.25mm.

[0067] Step S102, Negative-pitch stacking: The robotic arm picks up the second battery cell 2 and performs high-precision visual alignment, pressing the back electrode edge of the second battery cell 2 onto the light-receiving edge of the first battery cell 1 coated with buffer adhesive dots 4, forming a negative-pitch arrangement structure with a vertical overlap of 0.8mm between the edges of the two battery cells. During this process, the uncured buffer adhesive dots 4 are located in the clamping gap formed by the first battery cell 1 and the second battery cell 2, and are moderately wetted and spread under the slight bonding pressure of the two battery cells, wrapping the solder ribbon 3 within it to form a continuous battery string.

[0068] Step S103, Simultaneous Welding and Curing: The stacked battery string is conveyed at a constant speed through the multi-segment infrared light box radiation source 5. The infrared radiation source radiates infrared light energy to both sides of the battery string, causing the solder ribbons 3 in the overlapping area of ​​the battery cells to rapidly melt and connect with the solder on the surface of the main grid electrode of the battery cells within a 10-second travel cycle. During the welding heating section, the temperature of the battery cell joint area is maintained in the range of 170 to 180°C for 1.5 seconds. During this high-temperature thermal radiation process, while the solder ribbons 3 achieve electrical connection, the buffer adhesive points 4 between the two battery cells undergo a rapid hydrosilylation reaction within this temperature range and achieve complete cross-linking, realizing the simultaneous in-situ completion of welding and buffer adhesive curing.

[0069] Step S104, lamination and encapsulation: The multiple battery strings that have been welded and cured are arranged and positioned, and the upper layer adhesive film, lower layer adhesive film, front glass and back sheet material are applied. They are then transferred to a laminator and vacuum heated and laminated at 145°C. Subsequently, the aluminum alloy frame is assembled and the junction box is installed to obtain the finished photovoltaic module.

[0070] When a poor solder joint or a cracked cell is found in the battery string during step S103, the following rework and disassembly steps are performed (this step can also be used for repairing solar cells in later stages, and is not limited to the inspection stage):

[0071] Step S105, High-Temperature Heating: The battery string to be repaired is placed on a constant-temperature heating table preheated to 200°C. The heating and splitting tool 6 is used to uniformly heat the overlapping welding area of ​​the defective battery cell and the adjacent battery cell for 60 seconds. Under this temperature process, the polyester modified chain segments inside the buffer adhesive point 4 between the two battery cells undergo micro-phase separation and migrate to the bonding interface, resulting in a significant weakening of the adhesion between the adhesive layer and the silicon wafer and solder ribbon surface.

[0072] Step S106, Demolition without damage: Gently lift the defective cell with an anti-static vacuum pen. The defective cell is completely removed from the cell string. The silicon substrate is not cracked, and there are no strong adhesive residues on the solder ribbon and cell surface.

[0073] Step S107, Re-welding: Take intact and qualified battery cells, and repeat steps S101 to S103 to re-print adhesive dots on the steel plate, perform negative-pitch stacking, and infrared welding simultaneously to complete the in-situ non-destructive repair of the battery string. Table showing the viscosity and thixotropic index changes of the buffer adhesive prepared in Example 1 under open placement conditions at 20°C:

[0074]

[0075] Test data shows that under normal open conditions at 20℃, the thixotropic index of this buffer adhesive remains stable in the range of 5.31 to 6.02 within 72 hours, maintaining excellent anti-collapse performance and application flowability. It only undergoes natural and complete curing after 96 hours, exhibiting extremely high operational applicability and production convenience.

[0076] The physical and technological properties of the buffer adhesive and its component samples prepared in this embodiment were tested. The test results show that:

[0077] The Shore hardness of the cured adhesive layer is 30A;

[0078] The optical transmittance is 90.5% in the wavelength range of 380 to 1100 nm;

[0079] The 180-degree peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate at room temperature (25℃) is denoted as: The measured 180-degree peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate. =15N;

[0080] The peel force after being treated at 200℃ for 60 seconds is recorded as follows: The measured 180-degree peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate. =1.2N;

[0081] The rate of decrease in peel strength is denoted as Calculate according to the formula = (15-1.2) / 15×100%, calculated as follows =92.0%;

[0082] After trial production and defect detection of hundreds of battery strings, the zero microcrack rate of the battery cells after module lamination was 90.0%, and the success rate of rework and cell removal was 100%.

[0083] Example 2

[0084] Example 2 is an improvement on Example 1. The difference between this example and Example 1 is that the amount of heat-reducing modifier added is further optimized to improve high-temperature peeling efficiency.

[0085] The raw material composition of this cushioning adhesive, by parts by weight, includes:

[0086] 35 parts of vinyl-terminated polydimethylsiloxane with a dynamic viscosity of 20000 mPa·s at 25°C;

[0087] 15 parts of vinyl MQ resin with a dynamic viscosity of 25000 mPa·s at 25°C;

[0088] Two parts of hydrogen-containing polysiloxane with a hydrogen content of 1.2% by mass;

[0089] 35 parts of polyester-modified silicone resin;

[0090] 0.5 parts of platinum-vinylsiloxane complex;

[0091] 0.06 parts of methylbutynol, an alkynol inhibitor;

[0092] Specific surface area is 200m² 2 5 parts of fumed silica per g;

[0093] 1.5 parts of silane coupling agent γ-glycidyl oxypropyltrimethoxysilane.

[0094] The preparation method of the above-mentioned buffer gel includes the following steps:

[0095] The first step involves adding 35 parts of vinyl-terminated polydimethylsiloxane, 15 parts of vinyl MQ resin, 35 parts of polyester-modified silicone resin, 2 parts of hydrogen-containing polysiloxane, 2.5 parts of fumed silica with a specific surface area of ​​200 m² / g, and 1.5 parts of silane coupling agent into a planetary mixer according to the predetermined mass proportions. The mixture is stirred at 500 rpm for 15 minutes at room temperature until it is initially dispersed and uniform.

[0096] The second step is to add the remaining 2.5 parts of fumed silica to the mixer, start the vacuum system to evacuate to a vacuum level not higher than -0.09 MPa to remove volatiles, and fill with high-purity nitrogen to atmospheric pressure. Under nitrogen protection, stir at 1000 rpm for 60 minutes to fully wet and disperse the filler.

[0097] The third step involves adding 0.5 parts of platinum-vinylsiloxane complex and 0.06 parts of methylbutynol, circulating cooling water to control the temperature at 20°C, and stirring at 600 rpm for 120 minutes under nitrogen protection to obtain the single-component adhesive product.

[0098] The buffer adhesive from Example 2 was used to implement the laminated welding and rework process:

[0099] Step S201, Applying buffer adhesive: Using a precision steel plate printing screen, apply adhesive dots to the welding area at the edge of the first battery cell. The adhesive dots are 0.55mm wide, 1.8mm long, 0.25mm high, and 0.25mm from the edge.

[0100] Step S202, negative spacing stacking: The second cell is stacked on top of the first cell to form a negative spacing structure with an overlap width of 0.8mm, so that the uncured adhesive dots are held between the two cells and attached to the underside of the solder strip.

[0101] Step S203, simultaneous welding and curing: The battery string is fed into an infrared welding machine, and the welding area is heated to 175°C within 1.5 seconds. While the solder melts to form an electrical interconnect, the buffer adhesive is cross-linked and cured at high temperature.

[0102] Step S204, lamination and encapsulation: EVA film and glass components are laminated and framed on qualified battery strings.

[0103] Step S205, High-temperature heating: For defective battery strings, a constant-temperature heating table is used to heat the welded joint at 200°C for 60 seconds.

[0104] Step S206, Non-destructive cell removal: Use a suction pen to detach the defective battery cell, achieving non-destructive cell removal.

[0105] Step S207, Re-welding: Insert new battery cells and repeat steps S201 to S203 to complete the repair.

[0106] Performance test results show:

[0107] The Shore hardness of the cured adhesive layer is 28A;

[0108] Light transmittance is 91.3%;

[0109] 180-degree peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate at room temperature (25℃) =13N;

[0110] After being heated to 200℃ for 60 seconds, the 180-degree peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate... =1.0N, bond strength attenuation rate =92.3%;

[0111] The laminated cell has a zero microcrack rate of 89.5%, which meets the requirements for non-destructive cell disassembly and low microcrack encapsulation.

[0112] Example 3

[0113] Example 3 is an improvement on Example 1. The difference between this example and Example 1 is that the polyester-modified silicone resin is replaced with polyethylene glycol-modified silicone resin, and the amount is increased to 45 parts by weight, in order to verify the expanded applicability of the modified resin chemical category.

[0114] By mass parts, the raw material composition includes:

[0115] 35 parts of vinyl-terminated polydimethylsiloxane with a dynamic viscosity of 20000 mPa·s at 25°C;

[0116] 15 parts of vinyl MQ resin with a dynamic viscosity of 25000 mPa·s at 25°C;

[0117] Two parts of hydrogen-containing polysiloxane with a hydrogen content of 1.2% by mass;

[0118] 45 parts of polyethylene glycol-modified silicone resin;

[0119] 0.5 parts of platinum-vinylsiloxane complex;

[0120] 0.06 parts of methylbutynol, an alkynol inhibitor;

[0121] Specific surface area is 200m² 2 5 parts of fumed silica per g;

[0122] 1.5 parts of silane coupling agent γ-glycidyl oxypropyltrimethoxysilane.

[0123] The preparation method of the above materials is exactly the same as that of Example 1, including the steps of initial mixing, negative pressure vacuuming and nitrogen filling stirring, and adding catalyst and inhibitor at a controlled temperature of 20°C and stirring for 120 min.

[0124] The same steps S101 to S107 as in Example 1 are performed for adhesive application, negative pitch lamination, infrared welding synchronous curing, lamination, and high-temperature rework and disassembly processes.

[0125] Performance test results show:

[0126] The Shore hardness of the cured adhesive layer is 30A;

[0127] Light transmittance is 91.0%;

[0128] Peel strength between adhesive layer and monocrystalline silicon solar cell substrate surface at 25℃ and 180℃ (room temperature) =14N;

[0129] After heating at 200℃ for 60 seconds, the peel strength between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate =1.2N, bond strength attenuation =91.4%;

[0130] The component lamination yielded a 90.0% rate of zero microcracks, supporting non-destructive repair and disassembly.

[0131] Example 4

[0132] Example 4 is an improvement on Example 2. The difference between this example and Example 2 is that it verifies the effect of application height and process variation on the buffering effect.

[0133] Using the buffer adhesive prepared in Example 2, and with the exact same formulation, two sets of samples with printing heights of 0.15 mm and 0.40 mm were prepared by adjusting the cutout thickness and demolding gap of the steel plate printing screen. The battery strings and components were then assembled in strict accordance with the process flow from steps S201 to S207.

[0134] The test results show that:

[0135] When the height of the printed adhesive layer is controlled at 0.15mm, the Shore hardness after curing is 28A, the peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate at room temperature is 10N, and the peel force between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate after heating at 200℃ is 1.0N. The zero microcrack rate after module lamination decreases to 57.3%.

[0136] When the height of the printed adhesive layer is controlled at 0.40mm, the Shore hardness after curing is 28A, the peel force at room temperature is 15N, the peel force after heating at 200℃ is 2.0N, and the zero microcrack rate after component lamination is 83.1%.

[0137] The above comparison shows that if the adhesive layer height is too low, the deformation margin above the solder strip will be insufficient, resulting in a decrease in the zero microcrack rate; if the adhesive layer is too high, edge overflow will occur under the stacking pressure. Therefore, the adhesive layer printing height is preferably controlled in the range of 0.25 to 0.35 mm.

[0138] Example 5

[0139] Example 5 is an improvement on Example 1. The difference between this example and Example 1 is that it uses a pre-coated adhesive soldering process and an alternative combination of piezoelectric jet dispensing and hot air heating welding.

[0140] On the production line of copper solder strip, a precision piezoelectric jet dispensing valve is used to continuously spray a dot matrix of pre-coated buffer adhesive layer 7 on the area of ​​the solder strip to be overlapped for welding, with the adhesive dot height controlled at 0.28mm, to obtain pre-coated solder strip.

[0141] In the lamination welding process:

[0142] Step S501: Position and align the pre-coated adhesive ribbon with the first battery cell 1 and the second battery cell 2 and stack them with a negative pitch so that the pre-coated buffer adhesive layer 7 is in the clamping gap between the two battery cells.

[0143] Step S502: The wire is sent to the hot air convection welding station, where the welding of the solder strip to the main grid line and the high-temperature synchronous curing of the buffer adhesive are completed in 2 seconds under the blowing of hot air at 175℃.

[0144] Step S503: Perform encapsulation and hot air gun blowing and heating for chip removal and repair according to steps S104 to S107 of Example 1.

[0145] Test results show that the Shore hardness of the cured adhesive layer is 32A; the light transmittance is 90.8%; and the peel strength between the adhesive layer and the surface of the monocrystalline silicon solar cell substrate is [data missing - likely related to temperature and temperature]. =14N; After heating at 200℃ for 60s, the peel strength between the 180° adhesive layer and the surface of the monocrystalline silicon solar cell substrate is 14N. =1.1N, bond strength attenuation rate =92.1%; the zero microcrack rate after component lamination is 90.5%, supporting non-destructive repair and disassembly.

[0146] Comparative Example 1

[0147] The formulation, by weight parts, includes: 40 parts vinyl-terminated polydimethylsiloxane, 25 parts vinyl MQ resin, 2.5 parts hydrogen-containing polysiloxane, 0.5 parts platinum-vinylsiloxane complex, 0.06 parts methylbutynol, 7 parts fumed silica, and 2 parts silane coupling agent. No heat-reducing modifier was added. The preparation method and lamination welding process are the same as in Example 1.

[0148] Tests showed that the Shore hardness was 60A, the peel force at room temperature was 18N, and the peel force remained as high as 16N after being heated at 200℃ for 60 seconds, with a zero microcrack rate of 93.0%. Because the adhesive strength did not decrease at high temperatures, the silicon wafers cracked and broke during rework, making non-destructive wafer removal impossible.

[0149] Comparative Example 2

[0150] The formulation, by weight parts, includes: 50 parts vinyl-terminated polydimethylsiloxane, 10 parts vinyl MQ resin, 0.5 parts hydrogen-containing polysiloxane, 0.5 parts platinum complex, 0.06 parts methylbutynol, 4 parts silica, and 1 part coupling agent, aiming to obtain low hardness by reducing the crosslinking density. The preparation and process are the same as in Example 1.

[0151] Tests showed that the Shore hardness was 15A, the peel force at room temperature was only 3N, and the peel force after being heated at 200℃ for 60 seconds was 0.8N. Due to insufficient cohesion and hardness, the weld strip was subjected to direct rigid extrusion during lamination, resulting in a zero microcrack rate of only 2.8%, thus losing its buffering and protective function.

[0152] Comparative Example 3

[0153] The formulation, by weight parts, includes: 40 parts vinyl-terminated polydimethylsiloxane, 10 parts vinyl MQ resin, 1.2 parts hydrogen-containing polysiloxane, 0.5 parts platinum complex, 0.06 parts methylbutyninol, 6 parts silica, and 2 parts coupling agent. The preparation and process are the same as in Example 1.

[0154] Tests showed that the Shore hardness was 52A, the peel force at room temperature was 5N, the peel force after heating at 200℃ was 6N, the zero microcrack rate was 21.2%, and the silicon wafer was damaged during rework.

[0155] Comparative Example 4

[0156] The amount of polyester-modified silicone resin was significantly increased to 60 parts by weight, along with 35 parts of vinyl-terminated polydimethylsiloxane, 15 parts of vinyl MQ resin, 2 parts of hydrogen-containing polysiloxane, 0.5 parts of platinum complex, 0.06 parts of inhibitor, 5 parts of silica, and 1.5 parts of coupling agent. The preparation and process were the same as in Example 1.

[0157] Tests showed that the Shore hardness was 25A, the light transmittance decreased to 88.3%, the peel force at room temperature was only 2N, the peel force after heating to 200℃ was also 2N, and the zero microcrack rate dropped to 18.2%. Excessive heat-reducing modifier affected the continuous compatibility of the matrix resin, leading to defects in the cured crosslinking network and deterioration of mechanical support and buffering properties.

[0158] Summary table of overall performance test results for examples and comparative examples:

[0159]

[0160] Standard 180-degree peel tests were conducted on the cured samples of Examples 1 to 5 and Comparative Examples 1 to 4 using a universal testing machine. The test substrate was the edge area of ​​the light-receiving surface of a monocrystalline silicon photovoltaic cell. The hardness was measured using a Shore hardness tester, and the changes in adhesive force were recorded before and after heating at 200°C for 60 seconds. The peel force of Examples 1 to 5 at room temperature was measured to be between 10 and 15 N, which decreased to 1.0 to 2.0 N after high-temperature heat treatment, a reduction of more than 80%.

[0161] At the component end, a high-resolution electroluminescence defect detector was used to perform full-field microcrack scanning on the components after lamination. Statistical analysis showed that the zero microcrack rate of Examples 1 to 3 and Example 5 remained between 89.5% and 90.5%, which proved that a Shore hardness of 20 to 60A and a coating height of 0.20 to 0.40 mm can achieve stress relief effect on the laminated solder strips.

[0162] Meanwhile, during the rework phase, tests using soldering guns, constant temperature table heating, and hot air blowing confirmed that heating at 200℃ for 30 to 60 seconds can successfully peel off the silicon wafer without damage, supporting the practicality of this process in the manufacturing of negative-pitch tandem photovoltaic modules.

[0163] Regarding heat-reducing viscosity modifiers, as shown in Examples 1 and 3, polyester-modified silicone resin can achieve ideal high-temperature phase separation viscosity reduction effect. In addition, in other alternative technical solutions, polyethylene glycol-modified silicone resin, terminal long-chain aliphatic alkyl-modified silicone oil, fluoroalkyl-modified silicone resin, or the addition of thermally expandable microspheres can also be used as alternative solutions.

[0164] In terms of application method and carrier, buffer adhesive can be applied directly to the edge of the battery cell by steel plate printing or screen printing, or it can be pre-coated onto the surface of the welding strip by piezoelectric jet dispensing, pneumatic dispensing or roller coating to make pre-coated welding strip. In all these methods, when stacked with negative spacing, the uncured adhesive can be appropriately spread and wrapped around the welding strip by the mechanical clamping formed by the two battery cells.

[0165] In terms of welding and heating heat sources, in addition to infrared lamp box heat radiation, hot air convection heating, hot pressure head contact heat transfer or high frequency electromagnetic induction heating can all quickly activate the hydrosilicate addition reaction in 1 to 3 seconds within the temperature range of 160 to 185℃, and complete the synchronous in-situ integration of solder interconnection and buffer adhesive curing.

[0166] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the content of the present invention's specification shall also be included within the scope of protection of the present invention.

Claims

1. A buffer adhesive for stacking solar cells, characterized in that, By mass parts, it includes the following components: 30 to 60 parts of vinylsiloxane-based polymer; 1 to 10 parts of hydrogen-containing polysiloxane crosslinking agent; 15 to 45 parts of a heat-resistant anti-tack modifier, wherein the heat-resistant anti-tack modifier is an organosilicon-modified resin with high-temperature molecular chain rearrangement or phase separation characteristics. Catalyst 0.05 to 2 parts.

2. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The vinyl siloxane base polymer comprises vinyl-terminated polydimethylsiloxane and vinyl MQ resin; by weight, the vinyl-terminated polydimethylsiloxane comprises 30 to 50 parts, the vinyl MQ resin comprises 10 to 20 parts, and the sum of the weights of the two comprises 30 to 60 parts.

3. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The heat-reducing and viscosity-reducing modifier is selected from one or more of polyester-modified silicone resin, polyethylene glycol-modified silicone resin, terminal long-chain alkyl-modified silicone resin, and fluoroalkyl-modified silicone resin.

4. The buffer adhesive for stacking solar cells according to claim 2, characterized in that: The vinyl-terminated polydimethylsiloxane has a dynamic viscosity of 8,000 to 25,000 mPa·s at 25°C; the vinyl MQ resin has a dynamic viscosity of 10,000 to 35,000 mPa·s at 25°C; and the hydrogen content of the hydrogen-containing polysiloxane crosslinking agent is 0.3% to 2.5% by mass.

5. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The catalyst is selected from one of platinum-vinylsiloxane complex, platinum-cyclopentadienyl complex, or chloroplatinic acid-alcohol complex; the buffer gel also includes 0.01 to 1 part of inhibitor, which is selected from one of methylbutynol, phenylbutynol, 3,5-dimethyl-1-hexyn-3-ol, or ethynylcyclohexanol.

6. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The buffer adhesive also includes 1 to 15 parts of reinforcing filler, wherein the reinforcing filler has a specific surface area of ​​100 to 350 m². 2 / g of fumed silica; the buffer adhesive also includes 0.1 to 3 parts of silane coupling agent, wherein the silane coupling agent is selected from γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane or vinyltrimethoxysilane.

7. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The buffer adhesive also includes one or more of rheology modifiers, light stabilizers, or antioxidants, with an addition amount of 0.1 to 2 parts by weight.

8. The buffer adhesive for stacking solar cells according to claim 1, characterized in that: The cured buffer adhesive has a Shore hardness of 20 to 60A, and after being heated at a temperature of not less than 200°C for 30 to 60 seconds, the 180-degree peel strength between the adhesive layer and the surface of the battery cell substrate is reduced by more than 80% compared with the normal temperature state.

9. The buffer adhesive for stacking solar cells according to claim 8, characterized in that: The cured buffer adhesive has a Shore hardness of 25 to 35A and a light transmittance of more than 90% in the wavelength range of 380 to 1100 nm.

10. A pre-coated adhesive solder strip, characterized in that: The buffer adhesive for stacking solar cells according to any one of claims 1 to 9 includes a metal solder strip and a pre-coated portion or integral coating on the surface of the metal solder strip.

11. A method for laminating and welding solar cells, characterized in that, Using the buffer adhesive for solar cell stacking as described in any one of claims 1 to 9 or the pre-coated adhesive solder ribbon as described in claim 10, the method includes the following steps: Step 1, Applying adhesive or providing pre-coated solder ribbon: Apply the buffer adhesive to the edge welding area of ​​the first cell or the surface of the solder ribbon to be welded to form a buffer adhesive layer, or directly provide pre-coated solder ribbon with the buffer adhesive layer pre-coated; Step 2, Stacking: Stack the second battery cell with the first battery cell in a stacking manner, so that the buffer adhesive layer and the solder ribbon are in the stacking and clamping area between the first battery cell and the second battery cell to form a battery string; Step 3, simultaneous welding and curing: The battery string is fed into the welding equipment for heating. While the welding strip and the battery cell electrode are being welded, the heat from the welding process is used to simultaneously complete the high-temperature addition curing of the buffer adhesive layer. Step 4, encapsulation: The welded battery strings are laminated to obtain photovoltaic modules.

12. The method for stacking and welding solar cells according to claim 11, characterized in that: In step one, the adhesive application method is selected from one of the following: steel plate printing, screen printing, piezoelectric jet dispensing, pneumatic dispensing, or roller coating.

13. The method for stacking and welding solar cells according to claim 11, characterized in that: The buffer adhesive layer is arranged in the form of discrete adhesive dots, continuous adhesive strips, or an array pattern directly below the solder strip. The length of the buffer adhesive layer is not less than 1.2 mm, the width is 0.3 to 0.8 mm, and the coating height is 0.20 to 0.40 mm.

14. The method for stacking and welding solar cells according to claim 11, characterized in that: In step three, the heat source of the welding equipment is selected from one of the following: infrared lamp box heat radiation source, hot air convection source, hot pressure welding head, or induction heating source.

15. The method for stacking and welding solar cells according to claim 14, characterized in that: In step three, welding and curing are carried out using infrared lamp box thermal radiation. The peak temperature of the welding area is 160 to 185°C, and the heating time in the range of 170 to 185°C is 1 to 3 seconds.

16. The method for stacking and welding solar cells according to claim 11, characterized in that: If the battery string is defective, a rework and disassembly step is performed, which includes: The area to be repaired in the defective battery string is heated so that the buffer adhesive layer at the battery cell to be disassembled is heated to above 200°C and maintained for 30 to 60 seconds, inducing a heat-reducing and anti-sticking effect. Separate the battery cells to be disassembled from the battery string; The buffer adhesive is reapplied to the new replacement cell or solder strip, and the cells are stacked and then heated and welded again for simultaneous curing.

17. The method for stacking and welding solar cells according to claim 16, characterized in that: In the rework and disassembly step, a constant temperature heating table, soldering gun, hot air blowing, infrared radiation source or electromagnetic induction heating source are used to locally heat the area to be reworked.

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