Back contact battery 0BB interconnection method and integrated battery string preparation system

Abstract

The invention discloses a back contact battery 0BB interconnection method and an integrated battery string preparation system, and relates to the technical field of back contact battery non-main-grid interconnection. In order to solve the problems of high silver consumption, easy short circuit, silicon wafer bending due to heating, low production yield and the like during interconnection of back contact cells, the method comprises the following steps: preparing a polymer insulating composite film of which the two surfaces are coated with adhesives, positioning and punching, and then forming a welding strip-composite film-cell laminated structure with an 0BB low-temperature welding strip and a back contact cell; carrying out pre-hot pressing at 140-160 DEG C to realize alloying welding and bonding so as to form a battery string, and completing detection and repair before lamination; the corresponding system comprises an insulating strip welding strip unwinding device, a punching device, a typesetting device and a pre-pressing device, and automatic production is achieved. Insulation paste is replaced by positioning and punching of the composite film, the material and equipment cost is reduced, the yield is improved through detection and repair before lamination, silicon wafer bending is reduced, and the method is suitable for large-scale production of BC batteries and suitable for BIPV and other scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of back contact cell main grid-free interconnection, and particularly relates to a back contact cell 0BB interconnection method and an integrated cell string preparation system. BACKGROUND

[0002] BC cell is short for back contact solar cell. With the continuous innovation and development of photovoltaic technology, BC cell has become the focus of the industry due to its unique structure and excellent performance. The base type of BC cell is IBC cell, i.e. cross-finger back contact cell. The biggest feature of the cell is that the emitter level, surface field and metal electrode are all arranged on the back surface of the cell and are distributed in a cross-finger manner. This design makes the front surface of the cell free of any grid line obstruction, maximizes the use of incident light, reduces optical loss, and brings more effective generating area, thereby having high conversion efficiency and being more aesthetically pleasing in appearance. Whether it is a P-type or N-type cell, BC cell technology can be stacked to make a new type of cell. The cell with PERC stacked BC technology is PBC, the cell with TOPCon stacked BC technology is TBC, and the cell with HJT stacked BC technology is HBC. At present, the main technical routes include IBC, HBC, PBC, ABC, HPBC, etc.

[0003] Compared with the existing TOPCon and HJT technologies, BC cell has higher conversion efficiency. Its theoretical conversion efficiency limit is 29.1%, which is higher than that of TOPCon 28.7% and HJT 28.5%. The back electrode design simplifies the packaging process, supports full-automatic linear welding, reduces the risk of hidden cracks, and improves the deformation resistance by 48%. The front surface is free of grid line obstruction, and the prepared module has the characteristics of being aesthetically pleasing and having a single color, which is extremely suitable for BIPV. BC technology is compatible with P-type and N-type silicon wafers, and can further break through the efficiency limit by stacking, such as perovskite-IBC, and improve the light utilization rate to a higher waveband.

[0004] However, the development of the current BC cell technology also has certain difficulties.

[0005] 1. High silver consumption of BC cell: The electrode of BC cell is on the back surface, and the charge carriers need to pass through the entire cell to reach the electrode, resulting in high internal resistance. To reduce the resistance, the amount of silver needs to be increased and the silver grid line needs to be thickened, which increases the metallization cost and poses a challenge to the overall cost control.

[0006] 2. Current BC battery production yield is low: the back electrode interdigital electrode needs 2-3 laser slotting processes, which requires high equipment stability and process maturity level. However, the current laser precision is insufficient, and the battery back NP area contact appears short circuit problem, which restricts the production yield of BC battery. The front of BC battery has no grid line, and the positive and negative electrodes need to be accurately arranged and insulated on the back. It requires micron-level <5 μm patterned alignment precision, which is far beyond the PERC / TOPCon technology, usually >20 μm. At the same time, the back electrode intersects with each other, which makes the solder strip design, soldering process and packaging process need to be adjusted. These factors comprehensively affect the yield of BC battery, resulting in a relatively high scrap rate in the production process, increasing the production cost.

[0007] 3. High equipment cost: compared with TOPCon, the interdigital electrode on the back of BC battery needs additional laser slotting, plating and wet process equipment, and the precision requirement is higher. Since the BC battery technology is not yet fully mature, the related equipment has not been fully localized and scaled down, which significantly increases the cost of BC battery.

[0008] For the above BC battery technology difficulties, there are also certain challenges in the module packaging end, especially in the battery interconnection insulation treatment. Since the positive and negative electrodes are arranged in a cross pattern on the back of the BC battery, when using solder strips for series connection, it is necessary to isolate the positive solder strip from the negative grid line and the negative solder strip from the positive grid line. Local insulation treatment is very important.

[0009] Currently, there are mainly two schemes for flexible interconnection and rigid interconnection. The flexible interconnection scheme uses solder strips to directly connect multiple battery pieces, and there are two ideas for insulation treatment:

[0010] 1. Use insulating glue to isolate the solder strip and the surrounding fine grid;

[0011] 2. Make special solder strips with alternating conductive and insulating sections.

[0012] Taking the Longi scheme as an example, the conductive section of the same solder strip simultaneously welds the positive and negative regions of the adjacent two battery pieces. The rigid interconnection scheme uses metal pieces to connect adjacent battery pieces. The busbar of the same polarity terminates at the solder pad area on one side of the battery piece, and the metal piece connects the different polarity output terminals of adjacent battery pieces. The connecting piece is composed of conductive materials, which can be metal, alloy or compound containing metal elements. The metal piece has multiple holes in the middle as stress relief areas to improve the reliability of module connection. In this scheme, good insulation is required between the busbar and the different polarity connecting piece, as well as between the different polarity busbar convergence area to prevent short circuit. Regardless of which interconnection scheme, considering that BC battery is single-sided welded and silicon wafer is easily bent by heat, the process difficulty is increased. The current market mainstream string welding equipment cannot meet the demand, and a BC battery dedicated string welding machine is needed.

[0013] 0BB busbar-free technology is currently mainly applied to the field of HJT cell packaging, and currently there are mainly SmartWire, dispensing, welding + dispensing, film coating and other schemes.

[0014] Among them, the film coating scheme uses a skin film / integral film to bond and connect the cell piece and the welding strip in series. However, this scheme has the following problems:

[0015] 1. The skin film has high cost, low grammage, large shrinkage rate and unstable process;

[0016] 2. The front of the cell piece is shielded by an additional adhesive film, which reduces the light transmittance and affects the power of the module;

[0017] 3. The scheme is not conducive to detecting problem cell strings and repairing during the process after lamination, bonding and welding strip alloying, and EL testing after lamination is difficult to pass.

[0018] Therefore, how to provide a back contact cell 0BB interconnection method and an integrated cell string preparation system is a problem that those skilled in the art need to solve. SUMMARY

[0019] One object of the present application is to provide a back contact cell 0BB interconnection method and an integrated cell string preparation system. The present application can realize controllable contact of the welding strip with the positive and negative grid lines of the BC cell by positioning the high molecular insulating composite film, eliminate the use of high-precision equipment and processes for insulation using insulating glue, form a cell string before lamination, facilitate the discovery and solution of cell string problems, improve production yield, and at the same time, use high molecular insulating composite film to bond between the welding strip and the cell piece, which can reduce the bending of the cell piece during lamination. The present application designs a cell string integrated forming system, which makes the operation process simpler, provides a new series structure for the packaging of BC cells without busbars, and solves the problems of high cost of integral film / skin film, shielding of the front film, low light transmittance, and low yield of lamination alloying of the film coating scheme.

[0020] According to the back contact cell 0BB interconnection method and the integrated cell string preparation system of the present application, the following steps are included:

[0021] S1, preparing a high molecular insulating composite film: selecting PET, PP or PC film as a substrate, the thickness of the substrate is 100-200 μm; uniformly spraying polyurethane or acrylate adhesive on both sides of the substrate, the spraying thickness of the adhesive on both sides is the same, and is controlled to be 20-50 μm, forming a high molecular insulating composite film with a total thickness of 120-250 μm, wherein the adhesive is used to realize the bonding of the composite film with the welding strip and the cell piece;

[0022] S2, insulating composite film positioning punching: the high polymer insulating composite film is positioned and punched by a punching die, the punching die includes an upper panel and a lower panel, the upper panel is provided with a cylindrical protrusion, the lower panel is provided with a cylindrical groove matched with the protrusion, and the precise positioning of the composite film is realized through the embedding of the protrusion and the groove; the punching diameter is consistent with the grid width of the back contact battery, the hole position is one-to-one corresponding to the position of the positive and negative grid on the back of the battery, and the hole spacing is adapted to the positive-positive grid spacing, negative-negative grid spacing and the spacing between the adjacent two welding strips of the battery piece;

[0023] S3, laminating: the 0BB low-temperature welding strip is positioned and fixed by a traction clamp, the diameter of the 0BB low-temperature welding strip is 0.15-0.22mm; the surface of the welding strip is covered with the high polymer insulating composite film treated in step S2, so that the welding strip is aligned with the hole position of the composite film; and the back contact battery piece is positioned and covered on the composite film by a battery piece clamping mechanical arm, forming a three-layer laminated structure of "welding strip-high polymer insulating composite film-battery piece";

[0024] S4, preheating and pressing: the laminated structure is transferred to a hot pressing device, the hot pressing device includes a hot pressing plate with a silica gel material inside and a welding strip hot pressing positioning tool with a fluoroplastic material, the surface of the positioning tool is provided with a groove matched with the size of the welding strip to prevent the welding strip from deviating; preheating and pressing are performed at a temperature of 150-160℃, so that the welding strip contacts the positive and negative grid of the battery piece through the hole position of the composite film and realizes alloying welding, and at the same time, the welding strip, the composite film and the battery piece are bonded by the adhesive to form an integrated battery string; the appearance of the battery string is detected and EL tested, and the defective battery string is repaired, and the qualified battery string enters the subsequent laminating process.

[0025] Further, in step S2, the height of the cylindrical protrusion of the punching die is the same as the depth of the cylindrical groove of the lower panel, and the fitting gap between the protrusion and the groove is ≤2μm, so as to ensure the positioning accuracy of the punching position.

[0026] Further, in step S3, the 0BB low-temperature welding strip is a tin-plated copper strip or a silver-plated copper strip, and the surface of the welding strip is subjected to an anti-oxidation treatment.

[0027] Further, in step S4, the surface roughness of the silica gel hot pressing plate of the hot pressing device is ≤Ra0.8μm, so as to ensure the close fit with the surface of the battery piece.

[0028] An integrated battery string preparation system for realizing the back contact battery 0BB interconnection method of any one of claims 1-4, including in sequence connected insulating strip welding strip unwinding device, insulating strip punching device, insulating strip-welding strip-battery layout device and battery string pre-pressing device, and each device realizes linkage operation through a control system;

[0029] The insulation strip welding strip unwinding device comprises parallelly arranged insulation strip unwinding shafts and welding strip unwinding shafts, the insulation strip unwinding shafts are used for releasing high polymer insulation composite films, the welding strip unwinding shafts are used for releasing 0BB low-temperature welding strips, and both the unwinding shafts are provided with tension adjusting mechanisms to control the releasing speed;

[0030] The insulation strip punching device comprises a rack, a punching die mounted on the rack and a driving mechanism, the driving mechanism is a stamping assembly driven by a servo motor, and the punching interval can be adjusted according to the interval parameter of the battery piece grid lines;

[0031] The insulation strip-welding strip-battery layout device comprises a sliding rail, a moving platform moving along the rail and the moving platform, a traction clamp jaw mounted above the platform and a battery piece clamping mechanical arm, the traction clamp jaw is used for clamping and positioning the welding strip, the moving platform is used for carrying the laminated structure, and the mechanical arm is used for grabbing the battery piece from the battery piece groove and positioning and placing the battery piece on the composite film.

[0032] The battery string pre-pressing device comprises a hot-pressing tool, upper and lower oppositely arranged hot-pressing plates, a pre-pressing heating plate and a welding strip hot-pressing positioning tool, the hot-pressing plate is internally made of silica gel, and the pre-pressing heating plate is used for providing a heating temperature of 140-160 DEG C.

[0033] Further, the diameter of the cylindrical protrusion of the upper panel of the punching die of the insulation strip punching device is 0.01-0.02 mm smaller than that of the cylindrical groove of the lower panel, so as to ensure the flatness of the punching edge.

[0034] Further, the surface of the traction clamp jaw of the insulation strip-welding strip-battery layout device is provided with a wear-resistant ceramic coating, and the thickness of the coating is 5-10 mu m, so as to reduce the wear on the surface of the welding strip.

[0035] Further, the welding strip hot-pressing positioning tool of the battery string pre-pressing device is made of polytetrafluoroethylene, and the thermal deformation amount thereof is less than or equal to 0.1 mm / m under the environment of 160 DEG C.

[0036] Further, the detection and repair unit arranged downstream of the battery string pre-pressing device further comprises an appearance detection camera, an EL tester and a repair workbench, so as to identify defects of the pre-pressed battery string and provide a repair operation space.

[0037] Further, the battery piece clamping mechanical arm C of the insulation strip-welding strip-battery layout device is provided with a vacuum suction cup, the material of the suction cup is nitrile rubber, and the diameter is 50-80 mm, so as to avoid damage to the battery piece during grabbing.

[0038] The beneficial effects of the present application are:

[0039] 1、The present application realizes the controllable contact of the welding strip and the positive and negative grid lines through the positioning punching design of the high polymer insulation composite film, saves the purchase cost of the insulating glue and the high-precision gluing equipment, reduces the equipment investment and maintenance cost, avoids the use of high-cost skin film / integral film, adopts the conventional substrate composite film such as PET / PP / PC, greatly reduces the material cost, and the composite film is only located at the back of the battery, does not block the front light receiving area, solves the problem of light transmittance reduction in the traditional film covering scheme, and ensures the power output of the assembly.

[0040] 2、The present application avoids the contact of the positive welding strip and the negative grid line through the micron-level positioning punching of the punching die, significantly reduces the short circuit risk, and directly forms a battery string after preheating and pressing, so that the problems such as welding strip deviation, virtual welding and hidden cracks can be found in advance through appearance detection and EL test, the repair rate of defective products is improved, and the batch loss caused by the traditional film covering scheme after lamination cannot be repaired is avoided.

[0041] 3、The welding strip and the battery piece are bonded through the high polymer insulation composite film in the present application, the composite film can buffer thermal stress during preheating and pressing, so that the silicon piece bending degree is reduced, the hidden crack risk is reduced, the preheating and pressing process can realize the alloying welding of the welding strip and the grid line at 140-160 DEG C, and the stable bonding of the composite film adhesive is formed, so that the anti-deformation ability and long-term reliability of the battery string are improved.

[0042] 4、The present application integrates the processes such as insulation strip unwinding, punching, lamination and preheating and pressing, and realizes linkage operation through the control system, reduces the process switching time, greatly improves the production rhythm, meets the demand of large-scale production, and is suitable for the back electrode structure of the BC battery without main grid, innovates the interconnection structure to adapt to PBC, TBC, HBC and other BC technical routes, and supports the subsequent expansion of perovskite-BC laminated battery, and has strong universality.

[0043] 5、The composite film and the welding strip are located at the back of the battery, do not block the front light receiving area, avoid the color uneven problem caused by the front adhesive film of the traditional film covering scheme, make the appearance of the assembly more beautiful, and better meet the appearance consistency requirement of the building photovoltaic integrated scene. DETAILED DESCRIPTION

[0044] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with embodiments of the present application, and do not constitute a limitation on the present application. In the drawings:

[0045] Figure 1 A back contact battery 0BB interconnection method step schematic diagram is provided for the present application;

[0046] Figure 2 An integrated battery string planar structure diagram is provided for the present application;

[0047] Figure 3The integrated battery string cross section structure diagram is provided for the application;

[0048] Figure 4 The integrated battery string preparation system structure schematic diagram is provided for the application;

[0049] Figure 5 The integrated battery string preparation system punching die plane structure schematic diagram is provided for the application;

[0050] Figure 6 The integrated battery string preparation system punching die cross section structure schematic diagram is provided for the application;

[0051] Figure 7 The integrated battery string preparation system preheating and pressing device structure schematic diagram is provided for the application;

[0052] Figure 8 The integrated battery string preparation system preheating and pressing device structure schematic diagram is provided for the application.

[0053] In the figure: 1, insulation strip unwinding shaft; 2, is the welding strip unwinding shaft; 3, insulation strip positioning punching device; 4, sliding rail; 5, traction jaw A; 6, traction jaw B; 7, cutter; 8, hot pressing tooling; 9, hot pressing plate; 10, moving platform A; 11, moving platform B; 12, battery piece clamping mechanical arm; 13, battery piece groove; 14, upper preheating and pressing heating plate; 15, lower preheating and pressing heating plate; 16, welding strip traction jaw; 17, welding strip hot pressing positioning tooling; 18, welding strip; 19, high polymer insulation composite film; 20, battery piece. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0055] The specific embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0056] Embodiment 1

[0057] As shown in the figure, the back contact battery 0BB interconnection method of the application comprises the following steps: Figures 1-3

[0058] ​S1, preparing a high polymer insulating composite film: selecting PET, PP or PC film as a substrate, the thickness of the substrate is 100-200 μm; uniformly spraying polyurethane or acrylate adhesive on both sides of the substrate, the spraying thickness of the adhesive on both sides is the same, and is controlled to be 20-50 μm, to form a high polymer insulating composite film with a total thickness of 120-250 μm, wherein the adhesive is used to realize the bonding of the composite film and the solder strip and the battery piece.

[0059] The positive and negative electrode grid lines of the back contact battery are distributed in an interdigital manner on the back surface, and if the solder strip contacts the electrode grid lines, it will directly cause short circuit, so insulation isolation is the core requirement of interconnection. The high polymer insulating composite film needs to meet the dual functions of insulation and bonding: the substrate provides an insulating barrier, and the adhesive realizes structural fixation. PET, PP or PC is selected as the substrate because these three materials have excellent insulating strength at a thickness of 100-200 μm, and can maintain dimensional stability in the long-term use environment of photovoltaic modules. The thickness of the substrate needs to be matched according to the system voltage, for example, a 100 μm substrate can meet the insulation requirements for a system below 300 V, and a 200 μm substrate is needed for a system above 600 V to reduce the risk of creeping and avoid insulation breakdown under high voltage.

[0060] The adhesive is polyurethane or acrylate, which is matched with the preheating and pressing process: it can partially cross-link at 140-160°C, with a gel rate of more than 60%, to realize the preliminary bonding of the solder strip, the composite film and the battery piece, and the bonding strength after complete curing is ≥5 N / cm, which can resist the thermal stress during lamination and use. The spraying thickness of the adhesive is strictly controlled to be 20-50 μm, and the insufficient thickness will lead to insufficient bonding force and may cause delamination, and the excessive thickness will easily overflow from the hole site during hot pressing, polluting the grid lines and increasing the contact resistance. In actual production, the spraying precision is controlled by a slot coater to ensure that the thickness deviation of both sides is ≤±2 μm, and there is no bubble or missing coating phenomenon.

[0061] S2, positioning and punching the insulating composite film: positioning and punching the high polymer insulating composite film by using a punching die, the punching die includes an upper panel and a lower panel, the upper panel is provided with a cylindrical protrusion, the lower panel is provided with a cylindrical groove matched with the protrusion, and the precise positioning of the composite film is realized by the fitting of the protrusion and the groove; the punching diameter is consistent with the width of the grid line of the back contact battery, the hole site is one-to-one corresponding to the position of the positive and negative electrode grid lines on the back surface of the battery, and the hole site spacing is adapted to the positive-positive grid line spacing, the negative-negative grid line spacing and the spacing between the adjacent two solder strips of the battery piece.

[0062] The punching accuracy directly determines whether a short circuit occurs, so the punching die must meet strict size requirements. The upper and lower plates of the die are made of Cr12MoV alloy material, which has a hardness of HRC58 or above after quenching treatment, ensuring the dimensional stability of the protrusions and grooves after long-term use. The diameter of the cylindrical protrusions on the upper plate is exactly the same as the width of the grid lines, for example, when the grid line width is 50 μm, the protrusion diameter is also 50 μm; the diameter of the grooves on the lower plate is 0.01-0.02 mm larger than that of the protrusions, forming a small gap to prevent the composite film from being deformed by extrusion during stamping, ensuring that the height of the burr on the edge of the hole is ≤5 μm, and preventing local short circuits caused by burrs.

[0063] The positioning process is achieved through a CCD vision system: the edge of the composite film is provided with a reference mark, which is aligned with the reference line of the die to ensure that the position deviation of the hole site from the positive and negative grid lines is ≤±1 μm. The hole site spacing needs to adapt to three parameters at the same time: positive-positive grid line spacing, negative-negative grid line spacing, and adjacent ribbon spacing. For example, when the positive grid line spacing is 2 mm, the negative grid line spacing is 2 mm, and the ribbon spacing is 3 mm, the horizontal spacing of the hole site is set to 2 mm, and the vertical spacing is set to 3 mm, so that the ribbon only contacts the corresponding grid line through the hole site, completely isolating the opposite grid lines.

[0064] S3, layering: the 0BB low-temperature ribbon is positioned and fixed by a traction clamp, and the diameter of the 0BB low-temperature ribbon is 0.15-0.22 mm; the surface of the ribbon is covered with a high-molecular insulating composite film treated in step S2, so that the ribbon is aligned with the hole site of the composite film; then a back contact battery piece is positioned and covered on the composite film by a battery piece clamping mechanical arm, forming a three-layer structure of "ribbon-high-molecular insulating composite film-battery piece".

[0065] The 0BB low-temperature ribbon is made of a tin-plated copper strip or a silver-plated copper strip with a diameter of 0.15-0.22 mm. A diameter that is too small will result in insufficient current-carrying capacity, and a diameter that is too large will easily cause hidden cracks in the silicon wafer during hot pressing. The thickness of the tin plating / silver plating layer is 5-8 μm, which can reduce the welding temperature and avoid thermal damage to the silicon wafer due to high temperature; the surface is passivated by chromate to form an oxidation-resistant film with a thickness of 10-20 nm, and the thickness of the oxidation layer is ≤15 nm after 72 hours of storage, ensuring the alloying effect during welding.

[0066] The layer positioning is achieved through the cooperation of multiple devices: the surface of the traction clamp is covered with a 5-10 μm wear-resistant ceramic coating, which not only prevents the wear of the plating layer of the ribbon, but also provides sufficient friction to prevent the ribbon from slipping, with a positioning accuracy of ±0.05 mm; the composite film is fixed by a vacuum suction platform to align the hole site with the center line of the ribbon; the battery piece clamping mechanical arm is equipped with a nitrile rubber vacuum suction cup with a suction force of 5-10 kPa, which ensures stable grabbing and avoids excessive suction force that may cause the silicon wafer to break. The parallelism deviation of the final three-layer structure is ≤0.02 mm / m, avoiding local stress concentration.

[0067] S4, pre-pressing and detection: the laminated structure is transferred to a hot pressing device, which includes a hot pressing plate with silica gel material inside and a solder ribbon hot pressing positioning tool with fluoroplastic material, and the positioning tool surface is provided with a groove matched with the size of the solder ribbon to prevent the solder ribbon from shifting; pre-pressing is carried out at a temperature of 150-160℃, so that the solder ribbon contacts the positive and negative grid lines of the battery sheet through the hole of the composite film and realizes alloying welding, and at the same time, the solder ribbon, the composite film and the battery sheet are bonded by the adhesive to form an integrated battery string; the appearance of the battery string is detected and EL test is carried out, and the defective battery string is repaired, and the qualified battery string enters the subsequent lamination process.

[0068] The pre-pressing process needs to balance the welding quality and silicon sheet protection: the hot pressing plate inside adopts silica gel material with a Shore hardness of 60-70, and the surface roughness is ≤Ra0.8μm, which ensures that the surface fit degree with the battery sheet is ≥99%, avoiding virtual welding caused by local insufficient pressure; the solder ribbon hot pressing positioning tool is made of polytetrafluoroethylene material, and the thermal deformation amount is ≤0.1mm / m at 160℃, the surface groove width is 0.02-0.03mm larger than the diameter of the solder ribbon, and the depth is 1 / 3 of the diameter of the solder ribbon, which not only limits the shift of the solder ribbon, but also avoids excessive extrusion leading to deformation of the solder ribbon.

[0069] The pre-pressing parameters are optimized: the temperature is 150-160℃, which ensures that the tin layer is melted to realize alloying, while avoiding silicon sheet thermal bending of >0.5mm, the pressure is 0.1-0.3MPa, which ensures close contact and no hidden cracks, and the pressure holding time is 10-15s. Under this process, the solder ribbon and the grid line form Ag3Sn alloy phase, and the bonding strength between the composite film and the two is ≥5N / cm, which meets the requirements of subsequent processing.

[0070] The detection link includes: appearance detection uses a 5 million pixel camera to scan and identify defects such as solder ribbon shift and composite film wrinkle; EL test applies 1.5 times open circuit voltage bias, and detects short circuit and virtual welding through an infrared camera. The defective battery string is transferred to the repair table, and after heating and softening the adhesive at 80-100℃, it is re-adjusted, and the repair qualified rate is ≥90%, which significantly improves the overall yield.

[0071] Example 2

[0072] Please refer to Figures 4-8 The present application provides a kind of integrated battery string preparation system for realizing the above-mentioned back contact battery 0BB interconnection method, including insulation strip solder ribbon unwinding device, insulation strip punching device, insulation strip-solder ribbon-battery layout device and battery string pre-pressing device in turn, each device is linked operation by PLC control system.

[0073] The insulation strip welding strip unwinding device as the starting link of the system bears the stable supply function of the polymer insulation composite film and the 0BB low-temperature welding strip. The device includes parallelly arranged insulation strip unwinding shaft and welding strip unwinding shaft, and the distance between the shaft centers is 300-500 mm to avoid mutual interference when the materials are released. The insulation strip unwinding shaft adopts the air inflation shaft structure, which can adapt to the composite film coiled material with a diameter of 300-600 mm, and the quick clamping and shaping of the coiled material are realized by adjusting the air pressure. The welding strip unwinding shaft is equipped with a magnetic powder clutch, and the output torque is controlled by PLC to realize stepless adjustment of the release tension of the welding strip. The release speed is monitored in real time by a photoelectric encoder, and the speed difference with the downstream device is controlled within ±0.05 m / min to prevent the welding strip from being stretched or relaxed.

[0074] The core of the insulation strip punching device is to ensure the accurate matching of the composite film hole position and the battery grid line. Its structure includes a rack, a punching die assembly, a servo drive system and a visual positioning unit. The rack is made of cast iron material and is treated by aging, and the flatness of the table surface is ≤0.05 mm / m, which ensures the stability of the die installation reference. The punching die assembly is composed of an upper die holder, a lower die holder and a guide column. The guide column is plated with chromium, and the gap between it and the guide hole of the die holder is ≤0.01 mm, which ensures that the coaxiality of the upper and lower dies during stamping is ≤0.005 mm. The gap between the cylindrical protrusion of the upper panel and the groove of the lower panel is ≤2 μm, and the height of the protrusion and the depth of the groove are both 0.3 mm, which ensures that there is no edge curling after stamping. The servo drive system adopts a servo motor equipped with a 16-bit encoder, with a positioning accuracy of ±0.001 mm. It can automatically adjust the stamping interval according to the input grid line spacing parameters, and the response time is ≤0.05 s. The visual positioning unit contains a 2 million pixel CCD camera and a telecentric lens, with a shooting frequency of 10 frames / s. By identifying the positioning mark of the composite film edge, the die position is corrected in real time to ensure that the deviation between the hole position and the mark is ≤±1 μm.

[0075] The insulation strip-welding strip-battery layout device is the key to realize the accurate superposition of the three-layer structure, and its structure includes a sliding rail, a double moving platform, a traction jaw assembly, a battery piece handling mechanism and a positioning visual system. The sliding rail adopts a linear module, and the moving platform is driven by a servo motor with a positioning accuracy of ±0.01 mm. The two work alternately to realize continuous layering. The traction jaw is made of aluminum alloy material, and the surface is sprayed with a 0.05 mm thick Al2O3 ceramic coating. The clamping surface is designed as an arc shape matching the welding strip, and the clamping force can be adjusted by a gas cylinder to prevent the welding strip from slipping and to avoid damaging the plating layer. The battery piece clamping mechanical arm adopts a four-axis linkage structure, and the end is equipped with a nitrile rubber vacuum suction cup. The suction cup is connected to a vacuum generator to ensure that the battery piece is not deformed when it is grabbed. The positioning visual system contains two industrial cameras, which shoot the positioning marks of the welding strip-composite film combination and the battery piece respectively. Through image processing algorithm, the offset is calculated, and the platform is fine-tuned to realize the alignment of the three.

[0076] The function of the battery string pre-pressing device is to complete the heat pressing curing and alloying of the laminated structure. The structure comprises a heat pressing frame, an upper and lower heat pressing plate assembly, a temperature control system and a pressure adjusting unit. The heat pressing frame adopts a section steel welded structure, and deformation is eliminated through pre-stressed tie rods to ensure that the parallelism of the upper and lower plates is ≤0.02 mm / m during heat pressing. A silica gel heating layer is embedded in the heat pressing plate, and the surface is covered with a 0.1 mm thick stainless steel sheet. The temperature uniformity of the heating area is ±2℃ (150-160℃), and precise temperature control is achieved through a PID temperature controller. The solder strip heat pressing positioning tool is made of polytetrafluoroethylene, and the surface is processed with a groove, with a gap between the solder strip of ≤0.02 mm to prevent the solder strip from shifting during heat pressing. The pressure adjusting unit adopts a servo electric cylinder, with a pressure output range of 0.1-0.3 MPa, a pressure holding time that can be set to 10-15 s, and real-time feedback through a pressure sensor to avoid hidden cracks in the battery sheet caused by overpressure.

[0077] The system also comprises auxiliary devices: a cutter that adopts a carbide blade and is driven by a cylinder to achieve cutting of the battery string, with the cutting length being settable through an encoder; a battery sheet groove that adopts an anti-static material and is internally designed with a buffer pad to avoid edge damage when the battery sheet is stored; a detection and repair unit that is equipped with a 5 million pixel appearance detection camera and an EL test device to judge defects in the battery string through an image recognition algorithm, and a repair workbench that is equipped with a heating plate to facilitate softening of the adhesive for secondary adjustment.

[0078] The devices are linked and controlled through a Siemens S7-1200 PLC, and the control program contains a manual / automatic mode. In the automatic mode, production orders are received through the MES system, and the parameters of the devices are automatically adjusted: the unwinding tension is automatically matched according to the material width, the punching pitch is switched according to the grid line parameters, and the heat pressing temperature and pressure are set according to the type of the solder strip. The system is equipped with a human-machine interface that can display the status of each device in real time, store the last 1000 pieces of traceable production data, and automatically stop and alarm when abnormalities such as tension overrun or temperature deviation occur, to ensure that the production process is stable and controllable.

[0079] Through the coordinated operation of the above system, efficient interconnection of the main grid-free BC battery sheet can be achieved: the hourly production capacity of a single production line is ≥200 strings, the short circuit rate of the battery string is ≤0.1%, the hidden crack rate is ≤0.5%, the yield is improved by ≥15% compared with the traditional insulation glue scheme, high-precision gluing equipment is saved, the equipment investment cost is reduced by about 30%, and the core technical problem in the interconnection process of the BC battery is solved.

[0080] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacements or changes to the technical scheme and inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A back contact cell 0BB interconnection method and integrated cell string preparation system, characterized in that, The method comprises the following steps: S1, preparing a high-molecular insulating composite film: selecting a plastic film such as PET, PP or PC as a substrate, the thickness of the substrate is 100-200 μm; uniformly spraying polyurethane or acrylate adhesive on both sides of the substrate, the spraying thickness of the adhesive on both sides is the same, and is controlled to be 20-50 μm, thereby forming a high-molecular insulating composite film with a total thickness of 120-250 μm, wherein the adhesive is used to realize the bonding of the composite film and the welding strip and the battery sheet; S2, positioning and punching the insulating composite film: positioning and punching the high-molecular insulating composite film by using a punching die, the punching die comprises an upper panel and a lower panel, the upper panel is provided with a cylindrical protrusion, the lower panel is provided with a cylindrical groove matched with the protrusion, and the precise positioning of the composite film is realized by the fitting of the protrusion and the groove; the punching diameter is consistent with the width of the grid line of the back contact battery, the hole position is one-to-one corresponding to the position of the positive and negative grid lines on the back of the battery, and the hole spacing is adapted to the positive-positive grid line spacing, the negative-negative grid line spacing and the spacing between the adjacent two welding strips; S3, laminating: positioning and pulling the 0BB low-temperature welding strip by using a pulling clamp, the diameter of the 0BB low-temperature welding strip is 0.15-0.22 mm; covering the high-molecular insulating composite film treated in step S2 on the surface of the welding strip to align the hole position of the welding strip and the composite film; and positioning and covering the back contact battery sheet on the composite film by using a battery sheet clamping mechanical arm to form a three-layer laminated structure of "welding strip-high-molecular insulating composite film-battery sheet"; S4, preheating and pressing: moving the laminated structure to a hot pressing device, the hot pressing device comprises a hot pressing plate made of silica gel and a welding strip hot pressing positioning tool made of fluoroplastic, the surface of the positioning tool is provided with a groove matched with the size of the welding strip to prevent the welding strip from deviating; preheating and pressing at a temperature of 140-160 ℃ to make the welding strip contact with the positive and negative grid lines of the battery sheet through the hole position of the composite film and realize alloying welding, and at the same time, the welding strip, the composite film and the battery sheet are bonded to form an integrated battery string by the adhesive; performing appearance detection and EL test on the battery string, and repairing the detected defective battery string, and the qualified battery string enters the subsequent laminating process.

2. The method and system of claim 1, wherein, In step S2, the height of the cylindrical protrusion of the punching die is the same as the depth of the cylindrical groove of the lower panel, and the fitting gap between the protrusion and the groove is ≤2 μm, so as to ensure the positioning accuracy of the punching position.

3. The method and system of claim 1, wherein, In step S3, the 0BB low-temperature welding strip is a tin-plated copper strip or a silver-plated copper strip, and the surface of the welding strip is subjected to anti-oxidation treatment.

4. The method and system of claim 1, wherein, In step S4, the surface roughness of the silica gel hot pressing plate of the hot pressing device is ≤Ra0.8 μm, so as to ensure the close fitting with the surface of the battery sheet.

5. An integrated battery string manufacturing system for implementing the back contact battery 0BB interconnection method of any one of claims 1-4, characterized by, The method comprises the following steps: The insulating strip and welding strip unwinding device comprises an insulating strip unwinding shaft and a welding strip unwinding shaft arranged in parallel, the insulating strip unwinding shaft is used to release the high-molecular insulating composite film, the welding strip unwinding shaft is used to release the 0BB low-temperature welding strip, and both the unwinding shafts are provided with a tension adjusting mechanism to control the release speed. The insulation strip punching device comprises a rack, a punching die mounted on the rack and a driving mechanism, the driving mechanism being a servo motor driven stamping assembly, which can adjust the punching interval according to the battery piece grid line spacing parameter; The insulation strip-bonding ribbon-battery layout device comprises a sliding rail, a moving platform moving along the rail and the moving platform, a traction clamp jaw mounted above the platform, and a battery piece clamping mechanical arm, the traction clamp jaw being used for clamping and positioning the bonding ribbon, the moving platform being used for carrying the laminated structure, and the mechanical arm being used for grabbing the battery piece from the battery piece slot and positioning and placing the battery piece on the composite film; The battery string pre-pressing device comprises a hot-pressing tool, upper and lower oppositely arranged hot-pressing plates, a pre-pressing heating plate and a bonding ribbon hot-pressing positioning tool, the hot-pressing plates being internally made of silica gel, and the pre-pressing heating plate being used for providing a heating temperature of 140-160 DEG C.

6. The integrated battery string preparation system of claim 5, wherein, The diameter of the cylindrical protrusion of the upper panel of the punching die of the insulation strip punching device is 0.01-0.02 mm smaller than the diameter of the cylindrical groove of the lower panel, so as to ensure the flatness of the punching edge.

7. The integrated battery string preparation system of claim 5, wherein, The surface of the traction clamp jaw of the insulation strip-bonding ribbon-battery layout device is provided with a wear-resistant ceramic coating, and the thickness of the coating is 5-10 μm, so as to reduce the wear on the surface of the bonding ribbon.

8. The integrated battery string preparation system of claim 5, wherein, The bonding ribbon hot-pressing positioning tool of the battery string pre-pressing device is made of polytetrafluoroethylene, and the thermal deformation amount thereof under the environment of 160 DEG C is less than or equal to 0.1 mm / m.

9. The integrated battery string preparation system of claim 5, wherein, The detection and repair unit is further arranged downstream of the battery string pre-pressing device, the detection and repair unit comprising an appearance detection camera, an EL tester and a repair workbench, which can identify defects of the pre-pressed battery string and provide a repair operation space.

10. The integrated battery string preparation system of claim 5, wherein, The battery piece clamping mechanical arm C of the insulation strip-bonding ribbon-battery layout device is provided with a vacuum suction cup, the suction cup being made of nitrile rubber and having a diameter of 50-80 mm, so as to avoid damage to the battery piece during grabbing.

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