LED chip is characterized by high heat in a minimal volume. The heat capacity of the LED itself, it must be the fastest heat conduction out, otherwise it will produce a high junction temperature. Heat leads to the chip outside, a lot of improvements in the outdoor LED spotlights chip structure.
In order to improve the heat dissipation of the LED chip itself, the most important improvement is the thermal conductivity of the better substrates. Early outdoor LED spotlights only Si silicon as the substrate. Later changed to sapphire as a substrate. The thermal conductivity of the sapphire substrate is not very good (at 100 ° C is about 25W / (mK)), Cree’s silicon carbide silicon substrate in order to improve the cooling of the substrate, its thermal conductivity (490W / (mK), nearly 20 times) than the sapphire. And sapphire silver plastic solid crystal, the thermal conductivity of the silver plastic is also very poor. Silicon carbide only drawback is the cost more expensive. Cree is the production of silicon carbide substrate led high bay lights.
Using silicon carbide as a substrate, can indeed greatly improve its heat, but its cost is too high, and patent protection. Recent domestic manufacturers began to use the silicon material as a substrate. Because the base of silicon materials not subject to patent restrictions. And the performance is better than sapphire. The only problem is the expansion coefficient of GaN and silicon that much difference, but prone to cracking, the solution is to add a layer of aluminum nitride (AlN) as a buffer in the middle.