A new heat dissipation structure and principle analysis of LED lamps

As a new generation of solid-state light source, Light Emittin Diode ( LED ) has many advantages such as long life, high efficiency, energy saving, green environmental protection, etc. It is widely used in display! With the development of technology, advanced technology is continuously applied to semiconductors. In production, in order to increase the luminous efficiency of LEDs, the cost continues to decline.

The core part of the LED is the PN junction. The injected electrons and holes convert the electrical energy directly into light energy when they are combined in the PN junction, but not all converted light energy can be emitted outside the LED, it will be in the PN junction and ring. Oxygen resin/silica gel is converted into thermal energy by the absorption sheet. This thermal energy has great side effects on the lamp. If it cannot be effectively dissipated, the internal temperature of the LED will increase. The higher the temperature, the lower the luminous efficiency of the LED, and the shorter the life of the LED. In severe cases, LED chips will fail immediately, so heat dissipation is still a huge obstacle to high-power LED applications.

Existing cooling technology

The existing heat dissipation technology is shown in Figure 1: 101 is a heat-dissipating aluminum profile; 102 is a thermal silica gel gasket/silicone grease; 103-106 is an aluminum substrate, wherein 103 is an aluminum plate, 104 is an insulating layer, and 105 is a copper-clad layer, 106 For the solder resist layer 201-204 to form an LED lamp, wherein 201 is an electrode, 202 is an LED base, 203 is a PN junction of the LED, 204 is a silica gel, and then the solder is soldered to the copper layer of the aluminum substrate using a solder paste as shown in FIG. The black arrow shows: the heat generated by the PN junction of the LED passes through the LED base, a solder paste layer, a copper layer, an insulating layer, an aluminum plate, a thermal conductive silicone gasket, a silicone grease, and a heat-dissipating aluminum profile, which is emitted in the air. process.

Schematic diagram of existing LED lamp heat dissipation structure

Figure 1 Schematic diagram of the heat dissipation structure of existing LED lamps

The thermal conductivity of the LED base is about 80W//mk; the thermal conductivity of the solder paste solder layer is greater than 60W/mk; the thermal conductivity of the copper-clad layer is about 40 OW/mk, and the thermal conductivity of the aluminum and aluminum profiles is about 200 W/mk, the insulating layer The thermal conductivity is about Iw/mk, and the thermal conductive silicone gasket/silicone grease is about SW/mk, but the closer to the PN junction of the LED, the higher the heat flux density, and the thermal conductive silicone sheet/silicone grease has the lateral thermal conductivity of the aluminum plate. Thus, the heat flux density of the insulating layer is much higher than that of the heat conductive silicone gasket/silicone grease. Therefore, it can be clearly seen that the heat dissipation bottleneck lies in the insulating layer of the aluminum substrate.

LED lamp cooling technology

Since the heat dissipation bottleneck is an insulating layer on the aluminum substrate, then for the thermoelectrically separated LED, the following new processing technology can be used to process the aluminum substrate, which greatly enhances the heat dissipation capability of the LED lamp as shown in FIG. 2: the original in the aluminum substrate Under the LED base, the copper layer and the insulating layer are removed by drilling, and the aluminum plate is exposed. However, the aluminum cannot be directly soldered, and the solder metal layer needs to be plated on the bare aluminum plate after repeated research and processing verification. The following processing techniques are adopted: firstly, zinc is deposited on the bare aluminum plate, nickel is plated on the zinc surface, and then copper is plated on the nickel, and finally the coating on the copper is sprayed with tin or immersion gold. The thermal conductivity is good, and the LED can be soldered on the aluminum plate after the above plating process.

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