The working environment of solar panels is different, and the requirements for the adaptability and weather resistance of solar panels are very strict, which requires solar panel manufacturers to control the quality when selecting raw materials. In all raw materials, the importance of junction boxes is very prominent.
As an important component of solar panels, the solar photovoltaic junction box is a connector between the solar cell array composed of solar panels and the solar charging control device. It is a cross-domain comprehensive design integrating electrical design, mechanical design, and material science, which provides users with a combined connection scheme of solar panels.
As a connector of solar panels, the main function of the solar photovoltaic junction boxes is to export the electric energy generated by solar panels through cables and protect the lead of solar panels from being eroded by the external environment. Due to the particularity of the use of solar panels, the solar photovoltaic junction box must be specially designed to meet the use requirements of solar panels.
Because copper has low resistivity, low power loss, cheaper price than silver, good ductility, and convenient processing, there are many copper parts in the junction box: the bus strip is composed of a copper substrate and surface coating with the purity of 99.9999%; The wiring terminal is made of copper with the chrome-plated surface; Diode pins are also made of copper with tin or chromium-plated surface; The cable is made of pure copper.
However, because copper is more active and easy to react with other substances, the protection of copper-containing articles is very important. The performance in the junction box is the waterproof and dustproof grade, heat dissipation performance, and so on.
Generation mechanism of copper green
Copper reacts with oxygen, carbon dioxide, water, and other substances in the air to produce substances with green color, commonly known as copper green.
Influence of copper green on solar panels
Aeruginosa will increase the contact resistance of the contact point, resulting in continuous heating at the point, consume the current generated by the solar panel, reduce the output power of the solar panel, improve the internal temperature of the junction box, accelerate the aging of the sealing ring and box body materials, accelerate the aging speed of the backplane and EVA in contact with the junction box, and affect the service life of the solar panel.
Causes of copper green
1. The junction box is not well sealed, resulting in water vapor in the box space, which combines with oxygen and carbon dioxide to produce aeruginosa. Poor heat dissipation will make the temperature in the box higher and accelerate the above reaction.
2. The copper surface coating falls off or is damaged. The place where copper green occurs is generally the contact point of two kinds of conductors, such as diode and wiring terminal, wiring terminal and bus strip, wiring terminal and cable, etc.
Taking the contact point between diode and terminal as an example, some manufacturers use mechanical crimping when installing diode, and the coating on the surface of diode or terminal is damaged and fallen off, exposing the copper substrate and being corroded by air.
Treatment measures
When selecting the junction box, the quality shall be controlled. The junction box with high material quality, good conductivity, high sealing, good heat dissipation, and reasonable design shall be selected, in which the sealing and heat dissipation is very important. As long as the air is isolated and the temperature is reduced, the possibility of producing Copper Green will be very small.
