The manufacture of crystalline silicon solar cells (modules) is mainly to connect many monolithic solar cells in series and parallel with interconnecting strips, and then tightly seal them with adhesives to protect the cells from being broken and the surface of the cells, electrodes and interconnects. not corroded.
Encapsulation is a key step in the production of solar cells. If there is no good packaging process, no matter how good the cells are, the best modules cannot be produced. The encapsulation of the battery can not only ensure the life of the battery, but also enhance the strength of the battery. The high quality and long life of the product are the keys to winning customer satisfaction, so the packaging quality of the component board is very important.
(1) Solar cell production process
Battery inspection – front welding – inspection – back connection – inspection – laying (glass cleaning, material cutting, glass pretreatment, laying) – lamination – deburring (edge removal, cleaning) – frame installation (gluing, installation of corner keys) , punching, framing, scrubbing excess glue) – welding junction box – high voltage test – component test – appearance inspection – packaging and storage.
(2) Guarantee of high efficiency and long life of photovoltaic modules
①Using high conversion efficiency and high quality cells.
② Use high-quality raw materials, such as: EVA with high cross-linking degree, encapsulant with high bonding strength [neutral polysiloxane (silicone) resin glue], and tempered glass with high light transmittance and high strength.
③Reasonable packaging process and rigorous work style.
Since solar cells are high-tech products, some details in the production process, such as should wear gloves instead of wearing them, should evenly brush the reagents and scribble, will seriously affect the product quality, so in addition to formulating reasonable processes, employees are serious and Rigorous attitude is very important.
(3) Introduction to the solar cell assembly process
①Battery test Due to the randomness of the cell manufacturing conditions, the performance of the produced cells is not the same. In order to effectively combine the cells with the same or similar performance, they should be classified according to their performance parameters. Battery testing is to classify the battery output parameters (current and voltage) by testing it to improve the utilization rate of the battery and make battery components with qualified quality. If one or several low-power cells are installed in the solar cell, the output power of the entire module will be reduced. Therefore, in order to minimize the loss of battery series and parallel connection, it is necessary to combine single cells with similar performance into components.
②Welding Welding generally connects 6 to 12 photovoltaic cells in series to form a “photovoltaic cell string”. Traditionally, silver flat wires are generally used to form the connectors of the batteries, and then they are connected by methods such as spot welding or welding with infrared lamps (using the thermal effect of infrared rays). Now generally use 60% Sn, 38% Pb, 2% Ag plated copper flat wire (thickness is 100~200μm). The joint needs to be processed by fire, infrared, hot air and laser. Because lead is toxic, an alloy of 96.5% copper and 3.5% silver is now increasingly used. However, when using this alloy for welding, it is required that the welding temperature should not be too high, and the welding time should not be too long. There should be a good fit and proper clearance between the welded joints, and the joints should be smooth, flat and firm. Cells connected in series are required to be evenly spaced and of the same color.
③Backside series connection Backside series connection is to connect 36 cells in series to form a module string. At present, the process generally used is manual. The positioning of the battery mainly relies on a template with 36 grooves for placing the battery slices. The size of the groove corresponds to the size of the battery. The position of the groove has been designed, and components of different specifications are used. With different templates, the operator uses an electric soldering iron and solder wire to solder the front electrode (negative electrode) of the “front battery” to the back electrode (positive electrode) of the “back battery”, so that 36 batteries are serially connected together and assembled in the assembly. The positive and negative electrodes of the string are welded to lead wires.
④Laminated laying After the back is connected in series and passed the inspection, the component strings, glass and cut EVA, glass fiber, and backboard are laid according to a certain level, ready for lamination. Coat a layer of reagent on the glass in advance to increase the bonding strength of the glass and EVA. When laying, ensure the relative position of the battery string and glass and other materials, adjust the distance between the batteries, and lay the foundation for lamination. Laying level (from bottom to top): glass, EVA, battery, EVA, glass fiber, backplane.
⑤ Component lamination Component lamination is to put the laid battery into the laminator, pump out the air in the module by vacuuming, then heat to melt the EVA, bond the battery, glass and backplane together, and finally cool down , remove the components. The lamination process is a key step in the production of components, and the lamination temperature and lamination time are determined according to the properties of EVA. When using fast-curing EVA, the lamination cycle time is about 25 minutes and the curing temperature is 150°C. It is required that the single cell in the laminated module has no cracks, no cracks, no obvious displacement, no bubbles or delamination channels in the EVA between the edge of the module and any part of the circuit, and the EVA has a good degree of cross-linking.
⑥ Trimming During lamination, after the EVA melts, it extends and solidifies to form burrs due to pressure, so it should be cut off after lamination.
⑦ Framed Frame the laminated battery components, which is similar to installing a mirror frame on the glass to increase the strength of the components, further seal the battery components, and prolong the service life of the battery. The gap between the frame and the glass assembly is filled with silicone resin. The frame is made of stainless steel or plastic. The module consists of a frame and a junction box. 1m per production? The energy consumption of the aluminum alloy frame will increase by 215kW h. In order to reduce costs, frameless photovoltaic power generation modules are becoming more and more common. The modules are generally secured to the support structure using clamping bolts, sometimes glued. The use of frameless modules greatly reduces energy requirements and CO2 emissions.
⑧Welding the junction box Weld a box at the lead on the back of the module to facilitate the connection between the battery and other devices or batteries.
⑨ High-voltage test High-voltage test refers to applying a certain voltage between the frame of the module and the electrode leads to test the withstand voltage and dielectric strength of the module to ensure that the module will not be damaged under harsh natural conditions (lightning strikes, etc.).
⑩ Component test and labeling The purpose of the test is to calibrate the output power of the battery, test its output characteristics, and determine the quality level of the components. The international IEC standard test conditions are AM1.5, 100MW/m², 25℃. It is required to detect and list the following parameters: open circuit voltage, short circuit current, working voltage, working current, maximum output power, fill factor, photoelectric conversion efficiency, series resistance, parallel resistance and I-U curve, etc. According to the test classification results, the photovoltaic modules after the label are distributed, and then they can be loaded into the warehouse.
