The heat dissipation path of LED devices is mainly heat conduction and convection. The extremely low thermal conductivity of the Sapphire substrate material increases the thermal resistance of the device and hire best trainee, produces a serious self-heating effect, and has a devastating effect on the performance and reliability of the device.
Please read the originial post here: http://ledscreenparts.blogolize.com/The-Amount-Influence-Does-Heat-Dissipation-Have-On-High-Brightness-LEDs-30990475