Improve the heat dissipation efficiency of the LED system

April 30, 2021

In order to improve the heat dissipation effect, a material with good thermal conductivity is often used as the heat sink. Among the common metals, silver has the highest thermal conductivity, but it is expensive. The commonly used heat sink materials are mainly aluminum and copper. Aluminum is cheap, has low density, is well processed, and has good thermal conductivity. In comparison, copper has a higher thermal conductivity than aluminum, and many heat sinks with superior heat dissipation are made of pure copper. However, copper materials are expensive, easy to oxidize, and have high processing costs. In order to reduce the cost of LED street lights, it is recommended to use aluminum. The high-power LED is fixed as a light source on the luminaire. If the heat of the LED cannot be effectively and timely transmitted to the surface of the casing, the accumulated heat will cause the temperature of the radiant heat sink to rise sharply, resulting in an increase in the temperature of the LED and increasing the probability of LED failure. The LED light decay is intensified and the life is shortened. Since the thermal conductivity of air is very low, when installing the LED, it is necessary to ensure that the contact surface is flat and the contact is good, and a layer of heat conductive material is uniformly and appropriately applied to the bottom of the LED substrate or the surface of the heat sink. Generally, a thermal conductivity silicone grease, a thermal silica gel or the like is used.

The addition of a thermal conductive coating on the LED luminaire system can improve the heat dissipation efficiency of the LED system. The higher the thermal conductivity of the material, the better the heat dissipation effect. The 3LED heat dissipation design is controlled according to the requirements. The maximum temperature of the junction temperature is controlled at 125 ° C, so that the ambient temperature is up to 45. It can be normal in the case of °C. The LED's own thermal resistance R is 12 ° C / W, thermal grease thermal resistance is 8 ° C / W, LED is mounted on a 3 cm × 3 cm metal circuit board, thermal resistance, when the total LED power is 1.17W (current is 70 heat calculation), the calculated maximum thermal resistance of the heat sink is about 15 ° C / W. For this purpose, three kinds of heat sinks are designed. The heat sink width is 25 mm, the base thickness is 4 mm, and the fin height is defined as 30mm. Radiator model weight (g) heat dissipation area maximum temperature thermal resistance, type B thermal resistance is lower than type A thermal resistance, type C thermal resistance is lower than type B thermal resistance, visible T-shaped fin The thermal resistance is smaller than that of the rectangular fin, and the thermal resistance of the triangular fin is lower than that of the T-shaped fin. It can also be seen that the thermal resistance of the heat sink is related to the heat dissipation area, and the heat dissipation area is larger under the same conditions. The lower the resistance, the more the number of ribs and the height of the ribs can be increased in order to increase the heat dissipation area. The heat dissipation design and reliability study of the LED street lamps can also be provided with jagged or semi-circular wave patterns on the fins.

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