HEAT DISSIPATION STRUCTURE AND PRINCIPLE ANALYSIS OF HIGH POWER LED ENERGY-SAVING TYPE

Because the core part of LED lamps is PN junction (p-type semiconductor and n-type semiconductor are made on the same semiconductor substrate through diffusion, and the space charge area is called PN junction at their interface), and the light energy is converted into heat energy by the absorption plate inside the PN junction and epoxy resin / silica gel, which is a huge side effect on lamps, It will make the internal temperature of LED lamps higher and lower, the brightness lower and lower, and the service life shorter and shorter. Therefore, good heat dissipation is the guarantee for the LED lamps to keep constant brightness and extend the service life.

Next, we introduce the packaging structure of high-power LED: 

Because we have higher and higher requirements for LED light source, in addition to different requirements for LED light output rate and light color, there are also different requirements for light intensity and other aspects. In order to meet the needs of customers and improve the packaging process, chip manufacturers also put forward higher requirements for the packaging plant, and design a packaging structure that can meet the needs of customers better, so as to improve the LED External light utilization.

Different application areas put forward higher requirements for LED light source, in addition to different requirements for LED light efficiency and color, and different requirements for light angle and light intensity distribution. This requires not only the upstream chip factory to develop new semiconductor materials, improve the chip manufacturing process, and design the chip that meets the requirements, but also the downstream package factory to put forward higher requirements, design the package structure that meets a certain light intensity distribution, and improve the external light utilization of LED. 

The existing heat dissipation technology is composed of the following parts: heat dissipation aluminum profile, heat conduction silicon film or heat conduction silicon grease, heat conduction ceramic film, insulating silicon film LED lamp, electrode, LED base, led PN junction.

The heat dissipation process of thermal conductive silica gel is as follows: the heat source from PN junction of LED goes through LED base to solder paste welding layer to copper coating layer, through insulation layer to thermal conductive aluminum plate, then to thermal conductive silicon film or thermal conductive silicone grease, and then the heat is transmitted to thermal conductive aluminum plate for emission, so the whole heat dissipation process is completed.

Generally speaking, the thermal conductivity of LED lamp base is about 80W / m.k; the thermal conductivity of copper layer is 400W / m.k; the thermal conductivity of aluminum plate is about IW / m.k; the thermal conductivity of silicon gasket or silicon grease for LED lamp is generally 0.8 ~ 5.0w/m.k, The closer to the PN junction of the LED, the higher the heat flow density is. In this way, the heat transfer silicone sheet / heat transfer silicone grease has the same transverse heat transfer temperature of the aluminum plate. The heat flow density of the insulating layer is higher than the heat flow density of the heat transfer silicone grease, so it can be seen that the most difficult heat transfer is the insulating layer of the aluminum plate.

Since the most difficult part of heat dissipation is the insulating layer on the aluminum plate, Then the copper coating and insulation layer shall be removed by drilling holes, so that the aluminum base plate can be exposed, zinc can be deposited on the exposed aluminum plate, nickel can be plated on the zinc surface, copper can be plated on the nickel, and then tin or gold can be sprayed on the copper. After processing, the coating has strong adhesion, good heat conduction, and LED can be welded to the aluminum plate after coating process. After welding, the heat from LED PN junction passes through LED base to solder paste welding block, then to aluminum plate, then to LED lamp thermal conductive silica gel gasket or thermal conductive silicone grease to conduct the heat to the thermal aluminum profile and then to distribute in the air. Since the thermal insulation layer with very small thermal conductivity is removed, the heat dissipation effect is greatly enhanced, and the temperature of LED base is reduced accordingly, Thus, the service life and stability of LED lamps are prolonged.