Analysis of heat dissipation problem of high power LED bulb
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Today's LED white light products are gradually being put into use in various fields, people are feeling the amazing pleasure brought by their high-power LED white light and are also worried about the practical problems of their existence! First of all, from the nature of high-power LED white light itself. High-power LEDs still have poor uniformity of illumination, and the life of the sealing materials is not long. Especially, the heat dissipation problem of LED chips is difficult to be solved well, and the application advantages of white LEDs cannot be exerted.
Secondly, from the market price of high-power LED white light. Today's high-power LEDs are still a kind of aristocratic white light products, because the price of high-power products is still too high, and the technology still needs to be perfected, so that high-power white LED products are not used by anyone who wants to use them. The following is a breakdown of the related issues of high-power LED heat dissipation.
In recent years, under the efforts of industry experts, several improvements have been proposed for the heat dissipation of high-power LED chips: 1. Increase the amount of luminescence by increasing the area of ​​the LED chip. 2. It is used to package several small-area LED chips. 3. Change LED packaging materials and fluorescent materials. So is it possible to completely improve the heat dissipation problem of high-power LED white light products through the above three methods? It’s awesome! First of all, although we increase the area of ​​the LED chip to obtain more luminous flux (the number of light beams per unit area per unit area is the luminous flux, unit ml), we hope to achieve the white light effect we want, is it big? Power LED white light cooling problem can not be solved? Of course it is not impossible to solve. In response to the negative problem of simply increasing the wafer area, LED white light manufacturers have improved from the surface of high-power LED wafers by improving the electrode structure and flip-chip structure by using several small-area LED chips. /W's high luminous flux has low luminous efficiency.
In fact, there is another way to effectively improve the heat dissipation of high-power LED chips. That is to replace the white plastic packaging material with silicone or plexiglass. Replacing the packaging material can not only solve the heat dissipation problem of the LED chip, but also improve the life of the white LED. I want to say that almost all high-power white LED products like high-power LED white light should use silicone as the packaging material. Why do you have to use silica gel as a packaging material in high-power LEDs? Because the absorption rate of silica gel to light of the same wavelength is less than 1. However, the absorption rate of light by the epoxy resin to 400-459 nm is as high as 45, and it is easy to cause serious light decay due to aging caused by long-term absorption of such short-wavelength light.
Of course, in the actual production and life, there will be many problems such as heat dissipation of high-power LED white light chips, because the more widely used applications of high-power LED white light, the more difficult problems will be solved! LED chips are characterized by extremely high heat generation in a very small volume. The heat capacity of the LED itself is very small, so it is necessary to conduct this heat out at the fastest speed, otherwise it will produce a high junction temperature. In order to extract heat out of the chip as much as possible, people have made many improvements in the chip structure of the LED. In order to improve the heat dissipation of the LED chip itself, the most important improvement is to use a substrate material with better thermal conductivity. The thermal resistance of Cree's LEDs is at least twice as low as that of other companies because they use silicon carbide as the substrate.
Even if the heat resistance from the wafer to the package material can be solved, the heat dissipation effect from the package to the PCB is not good, and the temperature of the LED wafer is also increased, and the luminous efficiency is lowered. So, just like Panasonic, in order to solve such problems, from 2005 onwards, white LEDs including circular, linear, and surface-shaped LEDs were integrated with the PCB substrate to overcome the possibility of appearing from the package to the PCB. Interruption of heat between the two.
Therefore, in the face of continuous improvement of current conditions, how to increase the heat resistance is also an urgent problem to be overcome at present. From all aspects, in addition to the problem of the material itself, it also includes from the wafer to the packaging material. The heat resistance, heat conduction structure, heat resistance of the package material to the PCB board, heat conduction structure, and heat dissipation structure of the PCB board all need to be considered as a whole.