In recent years, due to the advancement of technology and efficiency, the application of LEDs has become more and more extensive; with the upgrading of LED applications, the market demand for LEDs has also developed in the direction of higher power and higher brightness, which is also known as high-power LEDs. .
For the design of high-power LEDs, most of the major manufacturers currently use large-size single low-voltage DC LEDs as their mainstay. There are two approaches, one is a traditional horizontal structure, and the other is a vertical conductive structure. As far as the first approach is concerned, the manufacturing process is almost the same as that of the general small-sized die. In other words, the cross-sectional structure of the two is the same, but different from the small-sized die, high-power LEDs often need to operate at large currents. Below, a little unbalanced P and N electrode design will cause serious current crowding effect (Current crowding), which will not only make the LED chip not reach the brightness required by the design, but also damage the reliability of the chip.
Of course, for upstream chip manufacturers/chip makers, this approach has high process compatibility (CompaTIbility), and there is no need to purchase new or special machines. On the other hand, for downstream system makers, the peripheral collocation, Such as power supply design, etc., the difference is not big. But as mentioned above, it is not easy to spread the current uniformly on large-sized LEDs. The larger the size, the more difficult it is. At the same time, due to geometric effects, the light extraction efficiency of large-sized LEDs is often lower than that of smaller ones. . The second method is much more complicated than the first method. Since the current commercial blue LEDs are almost all grown on the sapphire substrate, to change to a vertical conductive structure, it must first be bonded to the conductive substrate, and then the non-conductive The sapphire substrate is removed, and then the subsequent process is completed; in terms of current distribution, because in the vertical structure, there is less need to consider the lateral conduction, so the current uniformity is better than the traditional horizontal structure; in addition, the basic In terms of physical principles, materials with good electrical conductivity also have the characteristics of high thermal conductivity. By replacing the substrate, we also improve the heat dissipation and reduce the junction temperature, which indirectly improves the luminous efficiency. However, the biggest disadvantage of this approach is that due to the increased process complexity, the yield rate is lower than that of the traditional level structure, and the manufacturing cost is much higher.
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