Effect of heat dissipation capacity of junction box on cost and long-term reliability

Publish Time:2019/8/15   Views:2539

     Crystalline silicon semiconductor devices follow a law that the reliability of semiconductor devices decreases by 50%[3] for every 10 degrees increase in temperature. The lower the operating temperature, the higher the reliability of the devices. Obviously, the better the radiation system of the junction box, the better the long-term reliability.
     Due to the improvement of battery efficiency, the bypass diode passes through a higher current and generates more and more heat in the working state. The softening temperature of the plastic PPO used to make junction boxes is only 190 degrees, which is no longer able to resist the high temperature generated when the diode is working. The junction box manufacturer has to use some glass fiber reinforced nylon material on the base to ensure the mechanical strength of the shell at high temperature. Therefore, the heat dissipation design of the junction box, not only can reduce the size of the junction box, but also can use the shell material at a suitable price, directly reduce the cost of the junction box material.
     In junction boxes, diodes account for the second highest cost. In order to reduce the high temperature caused by the high current of high efficiency batteries, current junction box manufacturers have to reduce the temperature of diodes by using groove process diodes or increasing chip size without changing the size and heat dissipation structure of the original junction box. But in fact, the diode is completely wrapped in silica gel and plastic junction boxes, and the heat dissipation effect of the groove process is not ideal. Increasing the area of the chip will reverse the cost of the junction box. Therefore, low thermal resistance junction boxes can not only ensure long-term reliability, but also reduce costs and ensure quality by using suitable area of diode chips and simple process diodes.