PV ribbon are an important part of every mainstream solar panel, used to interconnect solar cells and provide connections to junction boxes. PV ribbon are tinned copper strips with a width of 1-6 mm, a thickness of 0.08-0.5 mm and a flux coating thickness of 10-30 μM.
There are two forms of PV welding bars applied to PV modules: interconnection bars or busbars and PV busbars. In a typical silicon solar cell, both are required.
The interconnection strip is soldered directly to the silicon crystal to interconnect the solar cells in the solar panel. The interconnection strips carry the current generated by the solar cells to the PV busbar. The PV busbar is a hot-dipped, tinned copper conductor mounted on the periphery of the solar panel. The PV busbar connects the interconnection strips to the junction box. Thin film solar panels generally only require bus bars.
Photovoltaic solder bars are a key component of solar panels and are an important factor in improving the efficiency and durability of solar panels. The high efficiency and durability of a solar panel can only be achieved if a high quality PV welding rod is properly installed on the solar panel.
High-quality PV welding rods can also improve the productivity of solar panels and reduce the scrap rate. The quality of PV welding rods and their welding to solar cells is an important factor in ensuring the efficiency and durability of solar panels.
1. Currently, the welding rods available in the market are mainly divided into silver-containing and silver-free welding rods. In addition to being expensive, silver-containing solder bars have their own advantages.
1) Improving the metallurgical bond between the solder and the metal to be soldered. After welding, the mechanical strength and electrical conductivity will be better.
2) After adding silver, the melting point of ternary alloy is lower than that of binary alloy, and its solderability and fluidity are improved.
3) The resistivity will be reduced and the high temperature resistance will be improved.
2. The resistance of the electrode is mainly determined by the size and specification of the electrode itself and the material of the copper base material. The composition of the tin coating on the surface will not have a significant effect on the resistance of the solder bar.
Increasing the width or thickness of the electrode can reduce the resistance of the electrode. This improvement can be equally effective in both conventional soldering methods and new low-temperature joining methods such as conductive silver glue or conductive tape joining.
However, a solder bar wider than the width of the front electrode can block the incident light and cause current loss. We recommend using a thicker solder bar without affecting the yield.
3. Solar cells covered by solder bars cannot absorb sunlight. Some solder bar companies have introduced reflective solder bars. The front side of the solder bar is silver plated and embossed with a longitudinal groove structure.
This structure can reflect the light incident on the solder bar at an angle to the inner surface of the module glass layer and project it onto the cell surface after it is completely reflected at the glass-air interface. The captured light allows the module to generate additional power, which can theoretically increase the efficiency of the module by about 2%.
4. Key quality parameters of photovoltaic welding rods
The performance indicators of PV welding rods are important in their own right. The type and purity of the copper determines the electrical conductivity of the material and the maximum flexibility of the electrode. The composition of the flux, the thickness of the cover layer and the composition of the cover affects the quality of the solder joint and thus the durability of the solar panel.
The high ductility of the photovoltaic electrode is important to prevent the failure of the solder joint between the busbar and the interconnecting electrode. Such failures can occur due to elongation/tension caused by temperature oscillations during solar panel operation.
The continuous and sometimes particularly violent temperature oscillations make solder joints endure over the lifetime of the solar panel (25 years on average).
For most PV panel strip manufacturers, two parameters are critical, namely flexure and yield strength. Many PV strip manufacturers find it difficult to obtain a high level of strip flexibility while still ensuring its straightness.
Obtaining adequate flexibility and low curvature can mean the difference between winning and losing a supply contract. As a result, manufacturers must strive to improve their rolling, annealing, tinning and material handling technologies to meet the ever-increasing requirements of product performance specifications.
Thus, the impact of welding rods on component power generation lies not only in the design materials of the rods themselves, but also in the selection of the rods, the lamination process and the quality control of the rod production. We need to understand welding rods from all aspects, although the industry may be more concerned with packaging materials and solar cells.