The first phase in a photovoltaic module manufacturing line is joining the solar cells, which is done by a solar tabber and stringer, a totally automatic machine able to optimise the very delicate phase of stringing and tabbing.
The thickness of silicon wafer is 160 μm, the thickness of PV copper strip is 0.1 mm, the thickness of Sn alloy coating is 15 μm and 25 μm respectively. The physical properties of materials used in solar cell welding are shown in Table 6.
The ununiform temperature field, mismatched thermal expansion coefficient and local plastic deformation during welding are the root causes of residual welding stress. The influence of welding process on the yield of solar cells has been discussed above.
The shading area of the photovoltaic welding strip is reduced by reducing the width of the main grid line and the PV welding strip, and the total amount of light received by the solar cell is increased. However, the contact resistance of the whole PV assembly is too large, which increases the electrical loss of the photovoltaic module.
Connection of Cells in Photovoltaic Modules. As shown in Fig. 5, the solar cells in the modules with different surface structures of welding strips have no cracks, and there is no open welding, false welding and desoldering, which indicates that it can be used for the subsequent research.
The quality of welding strip will directly affect the current collection efficiency of photovoltaic module, so it has a great impact on the power of photovoltaic module. The so-called photovoltaic welding strip is to coat binary or ternary low-melting alloy on the surface of copper strip with given specification.