Research And Development Of High Performance Photovoltaic Copper Belt

Photovoltaic(PV) copper strip is an important hub of the solar cells, it plays the role to transmit and gather electricity. In order to improve the efficiency of solar battery in photoelectric effect, reducing the power loss in the transmission process is as significant as developing more efficient cells; Otherwise reducing the rate of silicon cells smash during welding can bring huge economic benefits. After several stages of hardworking in analysis and tests, we get following conclusions:(1) ANSYS, a finite element software, is used to simulation the cooling process of photovoltaic copper strip after hot dipping and the welding process of solar cells. Then combining with the researches that scholars do on relationship between plastic deformation of metal material and the material elastic modulus, we find well annealed copper strip with low surface hardness can reduce the stress that is caused by the residual stress in final copper strip product and suffered by crystalline silicon cells.(2) In order to ensure copper strip’s high conductivity and stability, the content of oxygen and amount of porosity must be reduced in the strip; Rolling process with low deformation rate in single pass is better conformed to the requirements of this paper, and with the purpose of better controlling in properties of final copper strip product, the finishing rolling rate need lower than 60%; The third party performance test results of final copper strip product which is annealed with 450℃x2h shows: the value of conductivity is 102.7%IACS, the value of tensile strength is 224 MPa, the value of micro Vickers hardness is 45.8 and the extension rate is 45%.(3) This test pilot phase is combined with laboratory research results and tested on the actual production line in the factory. After lots of experiments and fumble the actual production technology of PV copper strip is preliminarily made: internal and surface quality of photovoltaic copper strip which produced by optimized smelting and casting process are excellent(grain size is uniform and small, the amount of porosity and slag is few); Processing rate of every pass in initial roll should be distributed small and flat; Deformation in intermediate rolling is advisable to keep between 50% and 60%; Back tension is better to be controlled around 5KN when it is rolling the photovoltaic copper strip which thickness from 0.7mm to 1.0mm in finishing rolling; Copper strip which rolled to 0.7mm~1.0mm is well annealed after 400℃~450℃x7h annealing with bell type bright annealing furnace; Copper strip is well annealed when adopting 650x32~45m/min annealing treatment in intermediate annealing process with air cushion type annealing furnace; Final annealing is suitable to adopt 650℃x95m/min annealing treatment to anneal copper strip which deformation is 50.4% and thickness is 0.124 mm with air cushion type annealing furnace.(4) Combining the experience from intermediate test phase with the requirements of products on specifications, rolling technology of PV copper strip is slightly adjusted in industrial production. The performance of products is perfect: Cu purity of photovoltaic copper strip as high as 99.9953%, the content of oxygen is only 8PPM, the value of tensile strength is 223.67 MPa, the value of Vickers hardness is 46.7 and the surface roughness is 0.15μm.(5) Products produced in this test are highly praised by the users, and bring good economic benefit for the company.