In recent years, high-power LED lighting technology has achieved rapid development, especially the power and light-emitting efficiency of blue-light LED chips (including white LED chips) have been increasing, and the pace of LED lighting entering ordinary people's homes has become more and more clear. However, as the input power of the LED chip continues to increase, the requirement of large heat generation and high light output efficiency of the high power has put forward new and higher requirements for the heat dissipation performance of the LED chip. The selection of high-efficiency heat-dissipating substrate materials is an important solution to the high-power LED entering the lighting market.
The GaN light-emitting layer of the blue LED chip is usually obtained on a sapphire (Al2O3) substrate by MOCVD epitaxial growth technique. However, since sapphire has a low thermal conductivity and a thermal expansion coefficient that is far from that of GaN (as shown in Table 1), a large amount of participating shear stress is generated between the GaN layer and the sapphire layer during use. Directly causing cracks in the GaN layer, causing chip failure. The metal heat-dissipating substrate material has attracted more and more attention from foreign mainstream LED chip manufacturers due to its excellent characteristics such as low expansion, high thermal conductivity, and adjustable expansion coefficient.
For the fourth generation of LED chips, foreign mainstream LED chip manufacturers usually use the following two methods to solve the problems caused by the high power of the chip:
1. Vertical structure of the chip (as shown in Figure 1)
The design of the vertical structure of the chip on the metal substrate increases the heat dissipation capability of the LED chip itself, and increases the density of the light-emitting chip per unit area, thereby finally achieving the purpose of increasing the amount of light emitted.
Figure 1 Principle of high power LED chip for vertical structure design 
Table 1 Comparison of performance of various LED chip heat dissipation substrates
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For more information, please refer to the October issue of "High-tech LED-Technology and Applications"
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