First, the impact of PV ribbons on the components
PV ribbons are an important part of every major solar panel used to interconnect solar cells and provide connection to junction boxes. The PV ribbons are tin-plated copper ribbons with a width of 1-6 mm, a thickness of 0.08-0.5 mm, and a 10-30 μm thick flux coating.
PV ribbons are applied to photovoltaic modules in two forms: interconnect strips or busbars and PV busbars. Both are required in a typical silicon solar cell. The interconnects are soldered directly to the silicon crystals to interconnect the solar cells in the solar panel. The interconnect strip brings the current generated by the solar cell to the PV bus. The PV bus is a hot dip tinned copper conductor mounted around the perimeter of the solar panel. The PV busbar connects the interconnect strips to the junction box. Thin-film solar panels generally require only busbars.
The PV ribbon in the solar panel is a key component and an important factor in improving the efficiency and durability of the solar panel. The high efficiency and durability of solar panels can only be achieved with good PV ribbons that are properly installed in solar panels. High-quality PV ribbons can also increase solar panel production efficiency and reduce rejects. The quality of PV ribbons and their welding on solar cells are important factors in ensuring the efficiency and durability of solar panels.
1. Currently, the ribbons in the market are mainly divided into silver-containing and silver-free ribbons. Among them, the silver-containing ribbon has its own advantages in addition to its high price:
1) Increase the metallurgical bonding between the solder and the metal being welded. Mechanical strength and conductivity will be better after welding.
2) After the addition of silver, the melting point of the ternary alloy is lower than that of the binary alloy, and its weldability and fluidity are improved.
3) The resistivity will be reduced and the high temperature resistance will be improved.
2. The resistance of the ribbon is mainly determined by the size of the ribbon itself and the material of the copper substrate. The composition of the tin coating on the surface will not significantly affect the resistance of the ribbon. Increasing the ribbon width or thickness can reduce the ribbon resistance. This kind of improvement can play the same role whether it is for the traditional welding method or the new type of conductive silver adhesive or conductive tape connection and other low temperature connection methods. However, the ribbon wider than the width of the front electrode blocks the incident light and causes current loss. We recommend using thicker ribbons without affecting the fragmentation rate.
3, solar cells covered by the ribbon can not absorb sunlight, some ribbon company launched a reflective ribbon, the front of the ribbon is silver plated and rolled out of the longitudinal groove-like structure, this structure can be incident on the ribbon The light is reflected at an angle to the inner surface of the glass layer of the module and is totally reflected at the glass-air interface and then is projected back to the surface of the battery. The captured light energy allows the assembly to generate additional power, which can theoretically increase the module efficiency by about 2%.
4. Key parameters of PV ribbon quality
PV ribbon performance indicators are important in their own right. The type and purity of copper determine the conductivity of the material and the maximum softness that the ribbon can achieve. The flux composition, its cover layer thickness, and the cover component affect the quality of the solder joints, thus affecting the durability of the solar panel.
The high extensibility of the PV ribbon is important to prevent solder joint failure between the busbar and the interconnect ribbon, which may occur due to the extension/tension caused by temperature swings during the operation of the solar panel. Continuous, and sometimes extremely intense, temperature oscillations during the lifetime of solar panels have put solder joints under test for the lifetime of solar panels (averaging 25 years).
The two most important parameters for most PV ribbon manufacturers are the camber and yield strength. Many PV ribbon manufacturers find it difficult to achieve a high level of ribbon flexibility while maintaining the straightness. Obtaining sufficient softness and low curvature may mean the difference between winning and losing a supply contract. Manufacturers must therefore strive to improve their rolling, annealing, tinning, and material handling technologies to meet increasing product performance requirements.
Therefore, the effect of the ribbon on the power generation of the component is not only the design material of the ribbon itself, but also the selection of the ribbon, the lamination process, and the quality control of the ribbon production. We need to understand solder ribbons in all aspects, although the industry may put more eyes on packaging materials and cells.
Second, common welding band specifications
Automatic spool with tinned copper tape
◆ Copper base: imported refined toughness oxygen free copper/T2 copper, copper content ≥ 99.99%, conductivity ≥ 98%
◆ Copper base resistivity: oxygen-free copper ≤ 0.0165 Ωmm2/mT2 copper ≤ 0.0172 Ωmm2/m
â—† Coating composition: 62%Sn36%Pb2%Ag (optional)
â—† coating thickness: single-sided coating 0.01 ~ 0.05mm, uniform coating, surface bright, smooth.
◆Coating Melting Point:179°C
◆ Tensile strength: Soft state ≥25kgf/mm2 Semi-soft state ≥30kgf/mm2
◆ Ribbon elongation: soft ≥ 35% 3/4 soft ≥ 25% 1/2 soft ≥ 15%
◆width error: ±0.1mm
◆ Thickness error: Interconnection zone ±0.01mm, Convergence zone ±0.015mm
Lead-containing silver coated tin copper strip
◆ Copper base: imported refined toughness oxygen free copper/T2 copper, copper content ≥ 99.99%, conductivity ≥ 98%
◆ Copper base resistivity: oxygen-free copper ≤ 0.0165 Ωmm2/mT2 copper ≤ 0.0172 Ωmm2/m
â—† Coating composition: 63%Sn36%P2%Ag (optional)
â—† coating thickness: single-sided coating 0.01 ~ 0.05mm, uniform coating, surface bright, smooth.
◆Coating Melting Point:179°C
◆ Tensile strength: Soft state ≥25kgf/mm2 Semi-soft state ≥30kgf/mm2
◆ Ribbon elongation: soft ≥ 35% 3/4 soft ≥ 25% 1/2 soft ≥ 15%
◆width error: ±0.1mm
◆ Thickness error: Interconnection zone ±0.01mm, Convergence zone ±0.015mm
Lead tinned copper strip
◆ Copper base: imported refined toughness oxygen free copper/T2 copper, copper content ≥ 99.99%, conductivity ≥ 98%
◆ Copper base resistivity: oxygen-free copper ≤ 0.0165 Ωmm2/mT2 copper ≤ 0.0172 Ωmm2/m
â—† Coating composition: 63%Sn37%Pb,603%Sn40%Pb (optional)
â—† coating thickness: single-sided coating 0.01 ~ 0.05mm, uniform coating, surface bright, smooth.
◆ coating melting point: 183 °C, 190 °C
◆ Tensile strength: Soft state ≥25kgf/mm2 Semi-soft state ≥30kgf/mm2
◆ Ribbon elongation: soft ≥ 35% 3/4 soft ≥ 25% 1/2 soft ≥ 15%
◆width error: ±0.1mm
◆ Thickness error: Interconnection zone ±0.01mm, Convergence zone ±0.015mm
Lead-free environmentally friendly tin coated copper tape
◆ Copper base: imported refined toughness oxygen free copper/T2 copper, copper content ≥ 99.99%, conductivity ≥ 98%
◆ Copper base resistivity: oxygen-free copper ≤ 0.0165 Ωmm2/mT2 copper ≤ 0.0172 Ωmm2/m
â—†Coating composition: 96.5%Sn3.0Ag0.5%Cu,96.5%Sn3.5Ag (optional)
â—† coating thickness: single-sided coating 0.01 ~ 0.05mm, uniform coating, surface bright, smooth.
◆ coating melting point: 217 °C, 221 °C
◆ Tensile strength: Soft state ≥25kgf/mm2 Semi-soft state ≥30kgf/mm2
◆ Ribbon elongation: soft ≥ 35% 3/4 soft ≥ 25% 1/2 soft ≥ 15%
◆width error: ±0.1mm
◆ Thickness error: Interconnection zone ±0.01mm, Convergence zone ±0.015mm
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